MVC handler method detection ignores scoped targets in favor of proxies

Issue: SPR-11548
Introduced getFlashMapsMutex template method and optimized SessionFlashMapManager's locking

SessionFlashMapManager also clears the session attribute now when the given FlashMap List is empty.

Issue: SPR-11538
Added ASM-based tests for custom scoping annotations

Issue: SPR-11574
Upgraded to Tiles 3.0.3