DATAJPA-628 - Use a shared SpelParser instead of recreating it.

We now create and use a singleton SpelExpressionParser instance in JpaQueryFactory that is passed on to every created query.
Cleaned up ParameterBinder inheritance hierarchy by merging (and removing) ExpressionAwareParameterBinder into SpelExpressionStringQueryParameterBinder.
Removed SpelParserAwareEvaluationContextProvider