This CL adds more TypeScript types and inserts some instanceof checks to
ensure typing. The CL also selects es2018 as target and loads es6/es2018
libs for TypeScript types. This ensures that RegExp groups matching
results are properly typed.

Notry: true
Bug: v8:7327
Change-Id: I1a59a1047188a49579c975149b336cc232c05eef
Reviewed-on: https://chromium-review.googlesource.com/c/1396095Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58553}