Raise Webhook URI length limit from 255 to 2048
Summary:
2048 is arbitrary (as 255 was) and only enforced in the UI but not on a DB level.
Closes T16303
Test Plan:
* Run `./bin/storage upgrade`
* Check `./bin/storage status`
* Check `EXPLAIN phabricator_herald.herald_webhook;` and/or http://phorge.localhost/config/database/localhost/phabricator_herald/herald_webhook/ before and after
* Go to http://phorge.localhost/herald/webhook/edit/form/default/ and enter a long URI in the `URI` field before and after
Reviewers: O1 Blessed Committers, avivey
Reviewed By: O1 Blessed Committers, avivey
Subscribers: avivey, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T16303
Differential Revision: https://we.phorge.it/D26462