review comments from Sreekanth

review comments

Logic inside segment implementations has been
moved up the stack into scorch, so that fewer
methods are required in the API.

- Iterator() becomes AutomatonIterator(nil, nil, nil)
- RangeIterator(start, end) now computes an end key
  compatible with traditional inclusive start, exclusive
  end keys.  Then becomes:
  AutomatonIterator(nil, start, endExclusive)
- PrefixIterator(prefix) now computes an end key
  and becomes:
  AutomatonIterator(nil, prefix, prefixEnd)

NumericRangeSearcher updated to no longer require
the IndexReaderOnly interface.  This interface
was only used for non-scorch indexes, but only
scorch actually implemented it.  Removing this
also meant we can remove the OnlyIterator method
from the segment dictionary API.

this code was originally placed in the segment package,
however it is only used by scorch, and makes more sense
to be placed at this level

the empty postings iterator is now only used
by scorch's optimize.go, so it is relocated here

the uvarint ascending encode/decode is only used
by scorch, so it too is moved inside this package

the unadorned postings lists are only used by scorch
so they are relocated to this package

note: while doing this it was observed that 'go mod tidy' was
failing with an error.  this relates to the kvstores in the
blevex package which will needed to be updated separately.

this change addresses this by removing the config_* and
upsidedown/benchmark_* files which caused the problem.

this does not remove support for these kvstores, just
the build tag support.

also fixup some places we missed during refactor

* move the plugin interface into scorch

* rename scorch Plugin to SegmentPlugin

and related functions

* update to make all analysis take place in func() (#1508)

* update to make all analysis take place in func()

by making analysis take place inside a func() a
closure can be used to encapsulate all the index
specific details.  this allows the index API to not
know about scorch vs upsidedown analysis structures

* rewrite variable declaration for clarity

also update comment, per review feedback

* update to latest versions

selects latest versions compatible with these changes

* update Advanced() method

at the top-level of bleve, Advanced no longer knows about
K/V stores, instead it only returns reference to the internal
index implementation.

this will allow us to remove the Advanced() method from the
internal index implementation.

NOTE: users who previously needed to access the underlying
K/V store, will still be able to do so, but must first
type assert that the internal index impl is
*UpsideDownCouch and if it is, they can use that Advanced()
method directly

* relocate store pkg inside upsidedown (#1510)

* relocate store pkg inside upsidedown

since kvstores are a concept unique to the upsidedown index
implementation, the store folder should be relocated inside
of that package

* remove Advanced() method from scorch (#1511)

* remove Advanced() method from scorch

after the API is updated, scorch no longer requires
this useless method to satisfy the interface

* update to latest apis

also, place shared kvstore test code in this
module, not in upsidedown (avoids circular deps)

previous the FieldCache type was in the index package,
but it is only used by upsidedown, so we relocate it there.

this removes the top-level bleve err ErrUnknownIndexType
instead, now the upsidedown specific error is returned.

users who actually care and are checking for this error type
still can, only now it is defined in the upsidedown package.

this interface is only used by the searcher package, thus
it makes sense to define it there

the dump methods were only ever supposed by upsidedown
now, users of this method must type-assert that their reader
is from the upsidedown package, where these methods remain,
unchanged.

these cause circular dependencies and are easy for applications
to do themselves

* use the moved indexing options

* update analysis.TokenFrequency to use options (#1522)

* update analysis.TokenFrequency to use options

previously it used boolean, and future changes would
require additional booleans.  using options directly
keeps the function signatures cleaner.

* update to latest apis

* update to work with removed items

* update to latest api

instead use the interface exposed by index api

* update for latest renaming

* update to latest apis

one example required updating as it's custom sort contained a
tie (both fields with age 0).  upsidedown always returned the
results in a particular order, which was not guaranteed by scorch.
to address this, the exmaple has been updated to include the
doc id as an additional sort criteria (ensuring the original
order expected is kept by scorch)

* Adding configurable freq/norm processing

Useful for use cases where score relevancy isn't needed
for the search requests.

A special frequency value of zero/0 is used for skipping
the freq/norm.

* update to work with removed items (#1524)

* update to work with removed items

* update to latest api

* do not type assert on document or field (#1525)

instead use the interface exposed by index api

* update for latest renaming (#1527)

* update for latest renaming

* update to latest apis

* switch default index to scorch with latest zap (#1528)

one example required updating as it's custom sort contained a
tie (both fields with age 0).  upsidedown always returned the
results in a particular order, which was not guaranteed by scorch.
to address this, the exmaple has been updated to include the
doc id as an additional sort criteria (ensuring the original
order expected is kept by scorch)

* update to release candidate apis (#1531)

Co-authored-by: Marty Schoch <marty.schoch@gmail.com>

it appears that while moving files around I mistakenly
changed a copyright header, which was not my intention

Right now `MatchOperator` constants are ints and when you're trying to
assign them to a variable you get an int. If you try to use those
variables as operator you get the following error:

```
cannot use operator (type int) as type MatchQueryOperator in argument to q.SetOperator

```

So, to fix this problem we just need to create `MatchOperator` constants

* update to v1 apis and zapx versions

* update to v1.0.1 upsidedown_store_api

* make sort integration tests more precise

the upsidedown implementation would break tie
sort order in a predictable way, and some tests
inadvertely relied on this behavior.

these tests have been adjusted to use a more
specific sort order, breaking all ties, such that
the expected results no longer depend on
implementation details.