Fixed getTypeDifferenceWeight algorithm in ReflectionHelper, and removed unused argsRequiringConversion storage

Issue: SPR-11306
Removed javadoc references to non-accessible subclasses
Turned ArgumentsMatchKind and ArgumentsMatchInfo to package-visible
Removed Commons Lang references
Remove unused import in MockHttpServletRequestBuilderTests
ObjectUtils.isCompatibleWithThrowsClause supports varargs now
Introduced "spring.getenv.ignore" system property for preventing System.getenv calls

Issue: SPR-11297
Polishing
Introduced "globalInitializerClasses" next to the existing "contextInitializerClasses", applying to FrameworkServlets as well

Issue: SPR-11314
Polishing
checkNotModified needs to consider HEAD as well

Issue: SPR-11317
Added tests for context initializers on DispatcherServlet

Issue: SPR-11314
Polishing