Update TransactionTemplate#equals() and #hashCode()

[arne-vandamme]

Inspect the PlatformTransactionManager property as well.
Issues: SPR-16572

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[jhoeller]

I've implemented this slightly differently, with transaction manager equality just getting enforced for an actual TransactionTemplate to compare with and not affecting toString either; in fact, not even hashCode has to be overridden for common hashing scenarios (as long as it provides the same hash code for equal templates). Not least of it all for backwards compatibility reasons, this shouldn't sacrifice the use of template instances as plain transaction definitions. Thanks for the pull request, in any case!