Cleanup PHP for more recent versions

[Spuds]

Continuation of going through the controllers to "freshen" the php level in a few areas.

• use static on closures that don't need $this
  • arrow functions fn() => for some one line closures
  • replace those \ElkArte\AdminController\XYZ calls with an import and XYZ::class
  • some hardening
  • useless else removal
  • early returns
  • remove list()
  • cast ints in some of the queries
  • positive logic in some if

Fix some bugs and todo's along the way

[codecov[bot]]

Codecov Report

Attention: 778 lines in your changes are missing coverage. Please review.

Comparison is base (5f05d2c) 34.42% compared to head (5659aa4) 33.99%. Report is 2 commits behind head on development.

Files	Patch %	Lines
sources/subs/MaillistPost.subs.php	36.02%	87 Missing :warning:
sources/ElkArte/Maillist/MaillistPost.php	30.97%	78 Missing :warning:
sources/ElkArte/Controller/PersonalMessage.php	17.30%	43 Missing :warning:
sources/subs/ManageAttachments.subs.php	0.00%	40 Missing :warning:
sources/ElkArte/Controller/News.php	0.00%	28 Missing :warning:
sources/ElkArte/Maillist/MaillistTopic.php	54.83%	28 Missing :warning:
sources/subs/Maillist.subs.php	3.57%	27 Missing :warning:
sources/ElkArte/Controller/ModerationCenter.php	54.38%	26 Missing :warning:
sources/ElkArte/AdminController/ManageMembers.php	8.33%	22 Missing :warning:
sources/ElkArte/Controller/Post.php	28.57%	20 Missing :warning:
... and 58 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #3756 +/- ## ================================================= - Coverage 34.42% 33.99% -0.43% + Complexity 16583 16582 -1 ================================================= Files 434 436 +2 Lines 83942 84028 +86 ================================================= - Hits 28895 28566 -329 - Misses 55047 55462 +415 ```

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