[Post summit] Fix run tag pinning

[inlined]

This is not for a feature launching at the summit and does not need to be checked in until after we thaw.

Previously the run rewrites used a splat operator to convert from firebase.json to api types but they're no longer compatible. Instead I need to set tag to the TODO_TAG_NAME when pinTags is true explicitly.

Verified with firebase.json:

{
  "hosting": {
    "public": "public",
    "rewrites": [
        {
            "source": "/latest",
            "run": {
                "serviceId": "tags-test"
            }
        },
        {
            "source": "/tagged",
            "run": {
                "serviceId": "tags-test",
                "pinTag": true
            }
        }
    ],
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ]
  }
}

Deployed the site and then redeployed to tags-test. You can verify at: at: https://inlined-junkdrawer.web.app/tagged https://inlined-junkdrawer.web.app/latest