Add EGL factory

This allows clients to call GrGLInterfaces::MakeEGL()

See also http://cl/626087349

Bug: b/293490566
Change-Id: Ie093bba9c89cffb925dcf5aee317cf318a7efdc9
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/842504
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Owners-Override: Kevin Lubick <kjlubick@google.com>
8 files changed