test_planner: Get repo to source mapping using manifest Gitiles fetch

This removes the last (I think?) dependency the orchestrator had on
having a repo checkout. Previously the test planner needed to run
`repo list`, but with this change, it instead just fetches and parses
the snapshot.xml file from manifest-internal.

TEST=unit tests, local run

Change-Id: Ied8ae375664885df222e679654068a469ef8d721
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/test_planner/+/1619341
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
Commit-Queue: Sean Abraham <seanabraham@chromium.org>
Tested-by: Sean Abraham <seanabraham@chromium.org>
8 files changed
tree: 4b8375de250196259a63affdf37198fd91ae9028
  1. .gitignore
  3. cipd.yaml
  4. deploy_cipd.json
  5. deploy_cipd.sh
  6. src/