Firewall: Deprecate and remove savepoint actions

[Monviech]

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• I have read the contributing guidelines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• I am convinced that my issue is new after having checked both open and closed issues at https://github.com/opnsense/core/issues?q=is%3Aissue

Is your feature request related to a problem? Please describe.

This is not actively used in the GUI anymore and a remainder of the os-firewall plugin:

core/src/opnsense/mvc/app/controllers/OPNsense/Firewall/Api/FilterBaseController.php

Lines 303 to 304 in 593a591

	// XXX: Not directly used by GUI, should be removed at some point
	public function applyAction($rollback_revision = null)

core/src/opnsense/mvc/app/controllers/OPNsense/Firewall/Api/FilterBaseController.php

Lines 318 to 319 in 593a591

	// XXX: Not directly used by GUI, should be removed at some point
	public function cancelRollbackAction($rollback_revision)

core/src/opnsense/mvc/app/controllers/OPNsense/Firewall/Api/FilterBaseController.php

Lines 331 to 332 in 593a591

	// XXX: Not directly used by GUI, should be removed at some point
	public function savepointAction()

core/src/opnsense/mvc/app/controllers/OPNsense/Firewall/Api/FilterBaseController.php

Lines 348 to 349 in 593a591

	// XXX: Not directly used by GUI, should be removed at some point
	public function revertAction($revision)

Describe the solution you like

Mark as deprecated in 26.7 and remove in 27.1

Describe alternatives you considered

None

Additional context

None