Currently the Spring TestContext Framework looks up a
PlatformTransactionManager bean named "transactionManager". The exact
name of the bean can be overridden via @TransactionConfiguration or
@Transactional; however, the bean will always be looked up 'by name'.

The TransactionManagementConfigurer interface that was introduced in
Spring 3.1 provides a programmatic approach to specifying the
PlatformTransactionManager bean to be used for annotation-driven
transaction management, and that bean is not required to be named
"transactionManager". However, as of Spring 3.1.2, using the
TransactionManagementConfigurer on a @Configuration class has no effect
on how the TestContext framework looks up the transaction manager.
Consequently, if an explicit name or qualifier has not been specified,
the bean must be named "transactionManager" in order for a transactional
integration test to work.

This commit addresses this issue by refactoring the
TransactionalTestExecutionListener so that it looks up and delegates to
a single TransactionManagementConfigurer as part of the algorithm for
determining the transaction manager.

Issue: SPR-9604