The commit range that is associated with a CI build is used for a couple
of things (mostly related to payload-size tracking):
- Determine whether a size change was caused by application code or
  dependencies (or both).
- Add the messages of the commits associated with the build (and thus
  the payload-size change).

NOTE: The commit range is only used on push builds.

Previously, the commit range was computed based on the
`CIRCLE_COMPARE_URL` environment variable. With [CircleCI Pipelines][1]
enabled, `CIRCLE_COMPARE_URL` is no longer available and the commit
range cannot be reliably detected.

This commit switches `CI_COMMIT_RANGE` to only include the last commit.
This can be less accurate in some rare cases, but is true in the
majority of cases (on push builds). Additionally, it stores the CircleCI
build URL in the database along with the payload data, so the relevant
info can be retrieved when needed.

[1]: https://circleci.com/docs/2.0/build-processing

PR Close #32537