[SPR-8386] Polishing SmartContextLoader SPI; AnnotationConfigContextLoader now only considers static inner classes annotated with @Configuration as configuration classes.

- introduced processContextConfigurationAttributes() method in SmartContextLoader SPI
- refactored AnnotationConfigContextLoader, AbstractContextLoader, AbstractGenericContextLoader, ContextLoaderUtils, and TestContext implementations to take advantage of the SmartContextLoader SPI, MergedContextConfiguration, and ContextConfigurationAttributes
- deleted ResourceTypeAwareContextLoader
- deleted ContextLoaderUtils.LocationsResolver and implementations
- moved context key generation from TestContext to MergedContextConfiguration

[SPR-7960][SPR-8386] Supporting declarative configuration of bean definition profiles in the TestContext framework:
- TextContext now works with MergedContextConfiguration instead of locations and loader
- TextContext now builds context caching key from MergedContextConfiguration
- Test context caching is now based on locations, classes, active profiles, and context loader
- TextContext now delegates to SmartContextLoader or ContextLoader as appropriate
- AbstractContextLoader now implements SmartContextLoader
- AbstractGenericContextLoader now sets active profiles in the GenericApplicationContext 
- Introduced integration tests for profile support in the TCF for both XML and annotation config

[SPR-6184] Introduced ResourceTypeAwareContextLoader interface and removed dependency on AnnotationConfigContextLoader in TestContext.