Spring Issue #24291 - Merge transactional attributes

Changes to spring-tx as discribed in #24291

Comment From: elab

@odrotbohm Since transaction attributes are merged in this new implementation, it could be used in spring-data as is (i.e. without reverting the order of lookups), what do you think?

Comment From: elab

Looking though Reference Documentation (Data Access part) 5.2.3 I couldn't find anything that had to be changed.

Comment From: jhoeller

It looks like we'll address both #24291 and #23473 through a new @TransactionConfig annotation, analogous to our existing @CacheConfig, or similar global settings which are not trying to rely on class-level @Transactional declarations (which brings in the undesirable implicit transactional-for-all-public-methods semantic whereas we only try to have certain settings shared for methods which are explicitly marked as transactional). From that perspective, we are not going to use a merging approach here.

Thanks for the PR, in any case!