Use Vector::uncheckedAppend() less in WebCore and use more efficient alternatives now that uncheckedAppend() has become an alias for append().
Pull request: https://github.com/WebKit/WebKit/pull/18804
Committed 269062@main (ba50d1bc34e9): <https://commits.webkit.org/269062@main> Reviewed commits have been landed. Closing PR #18804 and removing active labels.
<rdar://problem/116655812>