IsReceiverInitialRegExpPrototype, RegExpCreate

Bug: v8:8976
Change-Id: If1d2598a2c2f302704c25aa65826fa442e6b79a4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1866015
Commit-Queue: Z Nguyen-Huu <duongn@microsoft.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64361}