Title: Hashtable of types for R2R modules

Title: Hashtable of types for R2R modules
Description: This change replaces the hashtable of types that we dynamically build at module load time with a statically built hashtable at crossgen time, for R2R modules. Typedef tokens and exported type tokens are stored in that hashtable, hashed by their full type name.

Changes include:
- Adding support for NativeFormat hashtables (NativeFormat hashtable reader and writer + supporting functionalities)
- Changes to prevent the allocation and building of m_pAvailableClasses and m_pAvailableClassesCaseIns for a R2R module
- Logic in crossgen to build the hashtable of types, using the NativeFormat (table saved to a new section)
- Refactoring the type lookup functions to return results in a HashedTypeEntry data structure, which supports token based results, as well as EEClassHashEntry_t* based results
- Changes/Cleanup to the ClassLoader::GetClassValue to support the new lookup type
- Fixed small bugs in the std implementation
- Fallback to old hashtable lookup algorithm supported for:
	1) Case insensitive type loading
	2) R2R image built with older version of crossgen (not having static hashtable)

Tested following scenarios:
	- Token based lookups
	- Type name based lookups (Type.GetType API), including case insensitive scenarios
	- Nested types
	- Forwarded types (and forwarded nested types), up to 2 levels of forwarding
	- Old R2R image created with previous version of crossgen