Enable GPU Process and UI side compositing by default.
Pull request: https://github.com/WebKit/WebKit/pull/12161
*** Bug 254791 has been marked as a duplicate of this bug. ***
<rdar://problem/107461098>
Committed 262629@main (56f0f4203278): <https://commits.webkit.org/262629@main> Reviewed commits have been landed. Closing PR #12161 and removing active labels.