feat: data representations allow custom parsing and formatting of API fields.

See PR #2523. Most notable code changes:

- Load data representation casts into schema cache.
- Data representations for reads, filters, inserts, updates, views, over joins.
- `CoercibleField` represents name references in queries where coercion may be needed.
- `ResolverContext` help facilitate field resolution during planning.
- Planner 'resolves' names in the API query and pairs them with any implicit conversions to be used in the query builder stage.
- Tests for all of the above.
- More consistent naming (TypedX -> CoercibleX).

New: unit tests for more data representation use cases; helpful as examples as well.

New: update CHANGELOG with data representations feature description.

Fixed failing idempotence test.

New: replace date formatter test with one that does something.

Fixup: inadvertent CHANGELOG change after rebase.

Cleanup: `tfName` -> `cfName` and related.

Document what IRType means.

Formatting.

New: use a subquery to interpret `IN` literals requiring data rep transformation.

- With the previous method, very long queries such as `ANY (ARRAY[test.color('000100'), test.color('CAFE12'), test.color('01E240'), ...` could be generated. Consider the case where the parser function name is 45 characters and there's a hundred literals. That's 4.5kB of SQL just for the function name alone!
- New version uses `unnest`: `ANY (SELECT test.color(unnest('{000100,CAFE12,01E240,...}'::text[]))` to produce a much shorter query.
- This is likely to be more performant and either way much more readable and debuggable in the logs.

postgrest.cabal

@@ -49,6 +49,7 @@ library
                       PostgREST.SchemaCache.Identifiers
                       PostgREST.SchemaCache.Routine
                       PostgREST.SchemaCache.Relationship
+                      PostgREST.SchemaCache.Representations
                       PostgREST.SchemaCache.Table
                       PostgREST.Error
                       PostgREST.Logger