Add Vector::appendList() function which takes in a std::initializer_list and use it in a few places. Note that we already have a Vector constructor taking a std::initializer_list.
Pull request: https://github.com/WebKit/WebKit/pull/18603
Committed 268879@main (c1c9b7014e95): <https://commits.webkit.org/268879@main> Reviewed commits have been landed. Closing PR #18603 and removing active labels.
<rdar://problem/116491702>