Adding client param to context constructor so it can support other clients This change will make it possible for context classes to access multiple versions, e.g. GL version and GLES version Bug: angleproject:3661 Change-Id: I77a33d1c3ea3bffe94c64deb272219bbda1725a4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1689023 Commit-Queue: Clemen Deng <clemendeng@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>