Store in UIProcess whether VTB supports VP9 decode to query it only once in GPUProcess
Pull request: https://github.com/WebKit/WebKit/pull/2783
<rdar://97614473>
Committed 252902@main (76c46a7cbb12): <https://commits.webkit.org/252902@main> Reviewed commits have been landed. Closing PR #2783 and removing active labels.