Janitorial: Disparate cleanup tasks (#40200)

* Remove Phan suppression now that PHPDoc is correct in supported WP versions

* Remove WP 6.5 polyfill (see #38428)

* Remove is_callable check for wp_trigger_error()

* setMethods → onlyMethods

* static → const property

* Add type hinting

* Throw exception instead of triggering deprecation notice

* Remove now-unneeded CSS

* Updated comment

* Add future todo

* Remove fallbacks

* Add changelogs

* Remove composer downgrade logic

* CRM requires PHP 7.4 already

* Super Cache has previously required WP 6.5

* Vaultpress has previous required WP 5.2

* Get realpath of temp dir

* Fix changelogger tests

* Add changelogs

* Fix typo

* Adjust comment

* Simplify logic

* See if this sates tests

* Jetpack::is_connection_ready has been around in its current state since JP 9.7

* Remove checks for more long-present calls

* Clean up Phan suppressions

* Update changelog

Co-authored-by: Brad Jorsch <anomiex@users.noreply.github.com>

* Update changelog

Co-authored-by: Brad Jorsch <anomiex@users.noreply.github.com>

* Remove old comment

---------

Co-authored-by: Brad Jorsch <anomiex@users.noreply.github.com>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/11897114078

Upstream-Ref: Automattic/jetpack@d4ff610

composer.json

@@ -5,7 +5,7 @@
 	"license": "GPL-2.0-or-later",
 	"require": {},
 	"require-dev": {
-		"automattic/jetpack-changelogger": "^5.0.0"
+		"automattic/jetpack-changelogger": "^5.1.0-alpha"
 	},
 	"scripts": {
 		"build-development": "./tools/build",