Use a url-like source position format for emited defnition
locations. Hopefully this will make links clickable on codesearch.

Change-Id: I343c6bc3cc4f159d5e3974d7ec5af4a578aaf03a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3207887Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77261}