Refactors the gl::Program, gl::Compiler and gl::Query classes.

Bug: angleproject:2491
Change-Id: I96acecdc6af301a89201bd7f5222a180433e5eb2
Reviewed-on: https://chromium-review.googlesource.com/c/1289711Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>