Move relevant parser TypeComputer functionality into AISTypeComputer.

Notably, really only set types to column references and stop adding
casts.

parse/cast-2 looks inconsistent because BooleanNormalizer is the one
still adding casts and skips the non-literal.

test-coalesce.yaml partially disabled as concat was specially handled by
the old TypeComputer and functions don't work in general.
Gut FunctionsTypeComputer and leave only what it actually does
useComposers no longer does anything
merge nathanlws: Stop using the parser TypeComputer

Merge pull request #1565 from nathanlws/sql-layer/no-parser-type-computer
https://github.com/FoundationDB/sql-layer/pull/1565