Allow non-components in deployments to access the TransactionSynchronizationRegistry

As per https://jakarta.ee/specifications/transactions/2.0/apidocs/jakarta/transaction/transactionsynchronizationregistry, applications can look up the TransactionSynchronizationRegistry via java:comp/TransactionSynchronizationRegistry unless the application code that needs that is not part of an application component (e.g. in which case no access to java:comp namespace).

This is tracker for introducing a solution. Do any Jakarta EE implementations have a consistent way for non-component code to get access to the TransactionSynchronizationRegistry?

Start by reading the linked TransactionSynchronizationRegistry API documentation and the issue's question about non-component access to the java:comp namespace. Compare how Jakarta EE implementations expose this registry, then document a consistent solution and its specification impact; no files or tests are identified in the issue.

Written by the indexing model from the issue text.