Log repo.* config variables in git trace2 logger.

Bug: [google internal] b/181758736
Testing:
- Unit tests
- Verified repo git trace2 logs had expected data

Change-Id: I9af8a574377bd91115f085808c1271e9dee16a36
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/299182
Tested-by: Ian Kasprzak <iankaz@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Raman Tenneti <rtenneti@google.com>

main.py

@@ -297,6 +297,8 @@ class _Repo(object):
 
       cmd.event_log.FinishEvent(cmd_event, finish,
                                 result is None or result == 0)
+      git_trace2_event_log.DefParamRepoEvents(
+          cmd.manifest.manifestProject.config.DumpConfigDict())
       git_trace2_event_log.ExitEvent(result)
 
       if gopts.event_log: