New JPQL 3.2 and || as a String concat operator

[rfelcman]

This change contains following changes:

• New JPQL Grammar 3.2 (version matches upcoming Jakarta Persistence 3.2) and EclipseLink JPQL Grammar 4.1
• New JPQL String expression category with related classes (like arithmetic expression)
• New JPQL String operator || for string concatenation like JPQL CONCAT(....) function
  Tests are available in JPQL parser and JPA JSE test module
  EclipseLink issue is described at Implement new JPQLGrammar for upcoming Jakarta Persistence 3.2 #1885 and JPA specification request at the JPQL || operator for string concatenation jakartaee/persistence#397
  || operator is handled at JPQL level, but translated into SQL function CONCAT(...) as not every database supports || or is mentioned as OR logical operator (MySQL).

[lukasj]

LGTM