[infra] Use the actual project in src-side builder configs.

Currently, when chromium recipe code needs to refer to the project and
bucket for builders, it assumes that the project is the project of the
currently running builder and replaces try in the currently running
builder's bucket with ci. Neither heuristic is always accurate, but with
https://crrev.com/c/4345203, this change will provide an accurate
mapping in all cases when src-side configs are used.

Bug: 1424903
Change-Id: I932ebfb3703c2e876e3edfff6bce9b5aaed6e52d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4346116


Auto-Submit: Garrett Beaty <gbeaty@google.com>
Reviewed-by: Struan Shrimpton <sshrimp@google.com>
Commit-Queue: Struan Shrimpton <sshrimp@google.com>
Cr-Commit-Position: refs/heads/main@{#1118222}