Changes

Test: Remove dedicated mobile profile test, will be included in TestGLProfile01NEWT

Enhance ExtensionAvailabilityCache ; Expose extension count in GLContext (and clean up)

- GLContext
  - Expose isFunctionAvailable(), isExtensionAvailable(),
           getPlatformExtensionCount(), getGLExtensionCount()
  - sort methods a bit

ExtensionAvailabilityCache:
  - Favor StringBuilder instead of StringBuffer (faster)
  - Resuse set's
  - Hold dedicated counts of extensions, platform and GL

Fix ExtensionAvailabilityCache ; Enhance caching.

ExtensionAvailabilityCache regression / enhancement:
  - Set context version (w/o string) before caching.
    This is required since we query the ctx version.
    Regression from 4011e70eed8c88aee0fcd051a50ab3f15bb94f68

  - Remove GLContextImpl state. Only use the passed value at initialization.

  - Defined initialization, due to the 'new' cache/instantiation logic

Remove redundant GLContext profile bits:
  - CTX_OPTION_ANY: implicit if !CTX_OPTION_FORWARD
  - CTX_IMPL_ACCEL_HARD: implicit if !CTX_IMPL_ACCEL_SOFT

Cache key (ProcAddressTable, Extensions):
  - Mask out GLContext.CTX_OPTION_DEBUG | GLContext.CTX_IMPL_ES2_COMPAT,
    since they don't influence the cached values.

Simplify TestTransformFeedbackVaryingsBug407NEWT: Use 'in thread' ctx flow and debug context.