Upgrade/Install: Add plugin URL to the automatic update email.
For each automatic plugin update, both successful and failed, information about each plugin is included in the email upon completion of the process. This change adds the plugin URL, if known, to the information included for each plugin that was processed.
This change also adds unit tests to validate the email contents after various automatic plugin update scenarios.
Props JosVelasco, pbiron, oliverstapelfeldt, ChrisHardie, Ipstenu, dd32, peterwilsoncc, audrasjb, costdev.
Fixes #53049.