Simplify test includes & excludes in Gradle build

This commit aligns our include and exclude filters for test classes
with Gradle's standard patterns. Specifically, our patterns now end
with ".class" instead of ".*".

The aforementioned change makes the exclusion of inner classes
unnecessary. Thus, patterns for test classes ending with "TestCase" or
"TestSuite" have been deleted.

Furthermore, the include and exclude patterns previously used in the
spring-test module made it impossible for the
FailingBeforeAndAfterMethodsTests class in the 'testng' package to ever
be executed by the build. This has been addressed by renaming our JUnit
and TestNG variants of FailingBeforeAndAfterMethodsTests and moving the
TestNG variant into the 'junit' package so that it can be picked with
our standard include pattern for JUnit-based tests.