move SkRemoteGlyphCache.h to private

Chromium has been using the remote glyph cache for a few years now.
It's time to give it a proper home.

This is an intermediate CL. The old .h file includes the new .h file.
After I change the include paths in Chromium, I will delete the old
file.

Change-Id: Iaf00c46aa0698326c0bdec9a0eed218bcc3e334e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/482700
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
11 files changed