FrameCapture: Move compressed texture cache to shared location In support of tracking compressed texture data across multiple threads and contexts, move our cache to FrameCaptureShared. Make this accessible only via egl::ShareGroup, which will ensure unique texture IDs. Test: Asphalt 8 MEC Bug: b/150484427 Bug: angleproject:4048 Change-Id: I4e75b323d7aedc0333ceffba305439e54c4d6ac1 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2455266 Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>