Add more release assertion in the MemoryCache to help identify crash root cause.
Pull request: https://github.com/WebKit/WebKit/pull/15825
Committed 266050@main (59c4d69425e6): <https://commits.webkit.org/266050@main> Reviewed commits have been landed. Closing PR #15825 and removing active labels.
<rdar://problem/112233055>