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The doc includes a number of isolate links, but items in isolate expire
after 90 days. So this updates these to a set of new isolate links.
Hopefully by the time these new links expire, we'll be on RDB which will
have a slightly different debugging flow.

This also adds some tips on running the tests locally.

Bug: None
Change-Id: Ib6244f787d2a914b7c3a79aaba2a33b688d346c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522409Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824965}