[AutoDiff] NFC: Clean up `@transpose` attribute. (#28791)
Clean up `@transpose` attribute printing and parsing.
- Remove `Parser::parseTransposedParametersClause`.
- Instead, reuse `Parser::parseDifferentiationParametersClause` by
adding a `allowNamedParameters` flag.
- Remove `getTransposedParametersClauseString`.
- Instead, reuse `getDifferentiationParametersClauseString` by adding
a `DifferentiationParameterPrintingStyle` argument.
- Remove code from qualified declaration parsing utilities to reduce diff
with master.
- Revamp `test/AutoDiff/transpose_attr_parse.swift`.
Filed TF-1060: finalize `@transpose` type-checking rules.
Filed TF-1065: disallow qualified operators in `@transpose` attribute.
