FR: Cherry Pick promotion PRs should link to the CP Issue and relevant PRs

[samouri]

summary
AMP's old release issue trackers used to be a useful place to see how an RTV was deployed over time, and all of the CPs that were applied to it.

Ideally this new system could provide a similar view.
The CP Promote PRs should link to the relevant CP Issue and PRs.

For example, #159 should link to ampproject/amphtml#37715 and ampproject/amphtml#37671