Implement basic trigonometry functions

[jsternberg]

This adds support for math functions into the query language. Math
functions are special because they are transformations and do not access
the filesystem in the same way aggregate functions do. A transformation
takes one point and always outputs one point making it more similar to
binary expressions so these math functions follow the same rules as
binary expressions.

This also supports using math literals (so you can do sin(1)) and the
math functions can be used anywhere such as in a field or an expression.
Both of the following are supported:

SELECT sin(value) FROM cpu
SELECT value FROM cpu WHERE sin(value) > 0.5

Arguments are in radians. Degrees is not supported.

Fixes #9424.

• Provide example syntax
• InfluxData Documentation: issue filed or pull request submitted <influxdata/docs.influxdata.com#1457>

[jsternberg]

I'm likely going to refactor this to make use of #9511 instead of doing custom iterators. I think it will use less code and offer greater flexibility so we can shortly follow this with sqrt(x) and pow(x, y) along with related trigonometry functions like atan2(x, y).

The idea is that all of these functions will be implemented in this project (the query package) and they would not be present in the influxql project. But, for that, we need to expose an interface there. influxdata/influxql#13 is for that.

[jsternberg]

This has been refactored to make use of the math refactor in #9511. It's much simpler now and it will be easy to implement the other value transform iterators without advanced iterator nesting logic.

[stuartcarnie]

LGTM 💯