HSEARCH-1002 Running tests in SearchTestCaseJUnit4 with org.hibernate.testing.junit4.CustomRunner

Making sure that jgroups tests properly rebuild the configuration between tests (needed since JGroups channels get re-created)
HSEARCH-1002 Renaming SearchTestCaseJUnit4 to SearchTestBase and switching all remaining test classes extending from SearchTestCase to extend the new base class.

This way annotations like @Skip, @RequiresDialect, etc are consistently working with tests. Deleting now obsolete SearchTestCase. Updating sandbox module as well.
HSEARCH-1555 Making use of ClassLoaderService in HibernateSearchResourceLoader

- Removing stream based helpers from FileHelper to StreamHelper
- Refactoring AvroSerializationProvider
- Introducing Avro module specific Log interface