Prior to this patch, `new RegExp('a/b')` logs the following in
the DevTools Console:

    /a/b/

This is syntactically invalid.

This patch fixes this while simplifying regular expression printing
in general by leveraging `RegExp#toString`, instead of duplicating
the logic on the inspector side. This is possible thanks to the recent
work on making `RegExp#toString` more robust (v8:1982).

Bug: chromium:1202013, v8:1982
Change-Id: I14ccc1892f4a99361ad170fea608ace630740991
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2848463
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74169}