Fix parsing of single-character string literals in JPQL and EQL collection member expressions.

[jewoodev]

JPQL and EQL currently tokenize a single-character quoted string such as 'c' as CHARACTER, while other quoted strings are tokenized as STRINGLITERAL. The literal parser rule accepted STRINGLITERAL but not CHARACTER, causing a single-character string literal to fail when used as the left operand of MEMBER OF.

This change adds CHARACTER to the JPQL and EQL literal rules and covers the collection-member case with a shared query renderer round-trip test.

Jakarta Persistence allows a literal as the left operand of MEMBER OF, defines string literals as single-quoted strings without distinguishing single-character strings from longer strings, and itself uses 'Joe' MEMBER OF p.nicknames as an example.

• You have read the Spring Data contribution guidelines.
• You use the code formatters provided here and have them applied to your changes. Don’t submit any formatting related changes.
• You submit test cases (unit or integration tests) that back your changes.
• You added yourself as author in the headers of the classes you touched. Amend the date range in the Apache license header if needed. For new types, add the license header (copy from another file and set the current year only).

Closes #4278