[extensions] Convert App Window APIs over to use FrameTokens

- RenderFrame IDs were used to traverse the app window APIs. Use
blink::LocalFrameTokens instead.

Bug: 1502660
Change-Id: I2fa6c50fcd3fbb60fb54647dd9b80f88b4f7a099
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5089111


Reviewed-by: David Bertoni <dbertoni@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1234042}