Reorganize MakeRecAndEffects and SkScalerContext ctor

* This will allow the key descriptor and the device descriptor
  to be the same in SkRemoteGlyphCache.

* Simplifying SkRemoteGlyphCache descriptors will allow the
  rendering code in SkRemoteGlyphCache and the code in the GPU to
  be the same.

Change-Id: I1225c7e9017c05518ccadee1522751b94b1d97af
Reviewed-on: https://skia-review.googlesource.com/c/189582
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>