Drupal 9 Deprecated Code Report

Hi,

I'm Sorry I'm not around here alot. First, thanks for the contribution it still amazes me that someone is using what I initially started.

Second, I need to create a 9.x branch so you can submit the patch against that branch. But first, we need to fix the other tests because composer is failing in installing the dependencies. I kind of got back to do a bit of Drupal lately so I'll try to speed up this one.

#2 is a very nice patch, unfortunately it is breaking https://www.drupal.org/project/message_ui/issues/3068424#comment-13185860 which is needed.
I think that when everything will be cleared up, this patch should be one of the first to be committed (or one of the last) as it is changing many files and other patch must be insync with those changes

Adding patch with `core_version_requirement` in below files to make the module D9 compatible.
-> message_ui.info.yml
-> message_notify_ui.info.yml
-> message_ui_test.info.yml

Tested it on D8.9.3 as well as D9, installs successfully after applying the attached patch.

Re rolling Patch #5
Deprecated class changes in below files :
-> MessageNotifyForm.php
-> DeleteMultiple.php

Patch #6 works for me.
Installed successfully in D9 and works for D8 (8.9.3) as well.

Committed. Thanks all