[fuchsia] Clean up remaining references to Cast API migration.

* Remove no-longer implemented method definition in CastComponent
* Remove the old API to register MessagePorts in CastRunner.
* Remove integration and browser tests using former APIs.
* Adapt integration and browser tests to use the new API.

Bug: 953958
Change-Id: I192cd8453c3c730cb8ecab504884d46af5ad100b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1917327
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715869}
6 files changed