Introduce annotation to execute SQL scripts in the TCF

[sbrannen]

Prior to this commit, it was possible to execute SQL scripts
programmatically via ResourceDatabasePopulator, JdbcTestUtils, and
ScriptUtils. Furthermore, it was also possible to execute SQL scripts
declaratively via the XML namespace. However, it was not
possible to execute SQL scripts declaratively on a per test class or
per test method basis.

This commit makes it possible to declaratively configure SQL scripts
for execution in integration tests via annotations that can be declared
at the class or method level. Details follow.

• Introduced a repeatable @DatabaseInitializer annotation that can be
  used to configure SQL scripts at the class or method level with
  method-level overrides. @DatabaseInitializers serves as a container
  for @DatabaseInitializer.
• Introduced a new DatabaseInitializerTestExecutionListener that is
  responsible for parsing @DatabaseInitializer and
  @DatabaseInitializers and executing SQL scripts.
• DatabaseInitializerTestExecutionListener is registered by default in
  abstract base test classes as well as in TestContextBootstrapper
  implementations.
• @DatabaseInitializer and @DatabaseInitializers may be used as
  meta-annotations; however, attribute overrides are not currently
  supported for repeatable annotations used as meta-annotations. This
  is a known limitation of Spring's AnnotationUtils.
• The semantics for locating SQL script resources is consistent with
  @ContextConfiguration's semantics for locating XML configuration
  files. In addition, a default SQL script can be detected based
  either on the name of the annotated class or on the name of the
  annotated test method.
• @DatabaseInitializer allows for specifying which DataSource and
  PlatformTransactionManager to use from the test's
  ApplicationContext, including default conventions consistent with
  TransactionalTestExecutionListener and @TransactionConfiguration.
• @DatabaseInitializer supports all of the script configuration options
  currently supported by ResourceDatabasePopulator.
• @DatabaseInitializer and DatabaseInitializerTestExecutionListener
  support execution phases for scripts that dictate when SQL scripts
  are executed (i.e., before or after a test method).
• SQL scripts can be executed within the current test's transaction if
  present, outside of the current test's transaction if present, or
  always in a new transaction, depending on the value of the boolean
  requireNewTransaction flag in @DatabaseInitializer.
• DatabaseInitializerTestExecutionListener delegates to
  ResourceDatabasePopulator#execute to actually execute the scripts.

Issue: SPR-7655