Move MemberInfo to shared partition

[ghost]

There are really two easy changes here, just
to reduce CR overhead.

• CoreRt side of Replace MemberInfo.cs with the CoreRt version and move to shared partition. coreclr#10167

• Now that we have the shiny new IsConstructedGenericType
  api, let's use it...

[ghost]

Eh... pasted in the wrong commit text file. This was what it was supposed to be. I supposed I can fix in TFS before it gets merged to master. (Update: nope - don't seem to have permissions to alter changeset descriptions.)

Title:

 Implement TypedReference, FieldInfo.Get/SetValueDirect

Change Description:

 Notes:

• This does not include .Net Native support for the mkrefany/reftype/refvalue
  CIL instructions. (due to costing at this time.) This work
  is being done to unblock BinaryFormatter and other Reflection-related
  scenarios.

• At this time, the .Net Native toolchain cannot handle signatures with
  ELEMENT_TYPE_TYPEDBYREF. To work around this, TypedReference
  is intentionally placed in the wrong namespace
  (System.Reflection rather than System.)
  This allows us to do private testing (provided
  you build the test directly against CoreLib.dll)
  and not block this rather large commit on the toolchain work
  as that's not expected to happen imminently.

  • ByReference<> is broken right now and a fix isn't going to come around
    for a few weeks. So we added a private ByReferenceOfByte imposter
    that let's the rest of code think it's talking to a ByReference<>.

• Cleaned up the FieldAccessor type hierarchy to better
  support this change:

  LiteralFieldAccessor now derives from StaticAccessor.

  All the types that used to derive from StaticAccessor
  now derive from WritableStaticAccessor (comprises
  all static fields that aren't literals - this
  captures the fact that LiteralFieldAccessor is
  the only static field that doesn't call
  CheckArgument()).

  Hoisted the CheckArgument() calls into one place
  rather than in six. Aside from DRY, SetFieldDirect()
  on static fields needs to call the underlying UncheckedSet helpers
  while calling a different CheckArgument(). (Yay, consistency.)

  Removed the "obj" argument from the StaticFieldAccessor
  descendent's helpers. The fields are static, after all -
  the "obj" argument is vacuous and unused.