Metal: Restore load actions after attachment updates Framebuffer invalidation sets attachment load actions to MTLLoadActionDontCare. Restore them to MTLLoadActionLoad after content changes, which may be caused by texSubImage uploads. Fixes: * SimpleStateChangeTestES3.InvalidateThenSubUploadThenBlend * conformance2/renderbuffers/invalidate-framebuffer.html Bug: angleproject:7397 Change-Id: I8a1b223c92b1fd082f4961161efafaf6b60f8698 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4001808 Reviewed-by: Kyle Piddington <kpiddington@apple.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com>