This is a large refactor that replaces instances of "GLint location"
for uniform locations with "UniformLocation location". This boxed type
is similar to the ResourceID types that we use to capture resource IDs
more easily. Eventually this will give us a more portable replay.

Bug: angleproject:4411
Change-Id: I848e861c3956d95b6b953f57f8b6a2c4a676766f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2066117Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>