Fix revision mapping for bot_update.
Fix revision mapping for bot_update.

This adds support for printing arbitrary got_revisions from a revision mapping, either passed in (non-recipe bots) or hardcoded in (recipe bots).

BUG=261741

Review URL: https://codereview.chromium.org/217323009

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@261221 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build