R1:a9560479894f

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Summary:
Ref T11741. Fixes T10642. Parse and compile user queries with a consistent ruleset, then submit queries to the backend using whatever ruleset MySQL is configured with.

This means that `ft_boolean_syntax` no longer needs to be configured (we'll just do the right thing in all cases).

This should improve behavior with RDS immediately (T10642), and allow us to improve behavior with InnoDB in the future (T11741).

Test Plan:
- Ran various…