Serializes shaders and programs' states stored on CPU.

Adds shaders and programs serialization to serializeContext method so
that capture replay regresssion testing now compares the states of
shaders and programs too.

Bug: angleproject:4817
Change-Id: I026762ffcd85c9cf209f17d02025730aa286bd2f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2329830
Commit-Queue: Manh Nguyen <nguyenmh@google.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>