[Rest Api Compatibility] MovAvgPipelineAggregation

[joegallo]

Related to #51816 / #68905.

The moving_avg pipeline aggregation was deprecated in #29594 (6.4.0+) and removed via #39328, this PR adds back a nicer error message (but only in the presence of the relevant compatible-with=7 headers).

Quick action shot:

> GET /twitter-1/_search?pretty HTTP/1.1
> Host: localhost:9200
> User-Agent: curl/7.64.1
> Accept: application/vnd.elasticsearch+json;compatible-with=7
> Content-Type: application/vnd.elasticsearch+json;compatible-with=7
> Content-Length: 338
>
* upload completely sent off: 338 out of 338 bytes
< HTTP/1.1 400 Bad Request
< X-elastic-product: Elasticsearch
< Warning: 299 Elasticsearch-8.1.0-SNAPSHOT-bc6bceaca3bbfacfcc92b8a2480db5d38e1c5dec "Deprecated field [moving_avg] used, replaced by [Moving Average aggregation usage is not supported. Use the [moving_fn] aggregation instead.]"
< Warning: 299 Elasticsearch-8.1.0-SNAPSHOT-bc6bceaca3bbfacfcc92b8a2480db5d38e1c5dec "Moving Average aggregation usage is not supported. Use the [moving_fn] aggregation instead."
< content-type: application/json;charset=utf-8
< content-length: 452
<
{
  "error" : {
    "root_cause" : [
      {
        "type" : "parsing_exception",
        "reason" : "Moving Average aggregation usage is not supported. Use the [moving_fn] aggregation instead.",
        "line" : 14,
        "col" : 25
      }
    ],
    "type" : "parsing_exception",
    "reason" : "Moving Average aggregation usage is not supported. Use the [moving_fn] aggregation instead.",
    "line" : 14,
    "col" : 25
  },
  "status" : 400
}
* Connection #0 to host localhost left intact
* Closing connection 0

I expect that the vast majority of direct users of moving_avg have migrated over the last ~3.5 years of it being deprecated, and if you were using it indirectly via Kibana's Moving Avg then you've already been migrated to moving_fn for quite some time (see elastic/kibana#24702).

Side note: funnily enough, because moving_avg and moving_fn are so close together in terms of edit distance, 8.0.0 without the compat header still suggests the latter if you present it with the former. You still get an error, it's the same error you'd get for a typo like movnig_fn.

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)

[jakelandis]

Changes look good on the REST compat front, @not-napoleon - can you review the agg portion ?

one nit: can you add a comment to the Builder that it can be removed once support for compatibility with v7 is removed.

[not-napoleon]

For an aggregation that's intended to fail at parse time, this looks fine.

[not-napoleon]

I have never gotten a good answer for why we put BASIC-style line numbers on yml tests, but given that we do, 10 is already in use for histogram.

[not-napoleon]

Should we also @deprecate this?

[joegallo]

👍, c1d7a35