[IMP] Add bulk subscribe actions for auditlog rules

[drkpkg]

• Add server actions to trigger subscribe/unsubscribe from list view
• Ensure return type suits server action flow
• Support bulk handling without interfering with form buttons

[drkpkg]

@StefanRijnhart after the rebase from #3432 this feature is the only left.
This bulk feature is useful when you have a large number of rules to subscribe or unsubscribe.

Note: #3437 is discarded after the rebase from #3432.

[StefanRijnhart]

Thanks for the rebase!
Points of order:

• Next time, maybe keep the original PR, updating the title manually.
• [FEAT] does not conform to Odoo commit message prefixes (https://www.odoo.com/documentation/19.0/contributing/development/git_guidelines.html#tag-and-module-name), suggest [IMP].
• Please add the module name in the commit message, like [IMP] auditlog: add bulk subsccribe actions for rules.
• Please squash commits into one as they are intimately related.

Code review:

• Returning another action with soft-reload is not necessary. Odoo will already update the rules statuses without it. That means we can avoid adding the new methods as you can just call the existing subscribe/unsubcribe ones.
• The original subscribe method is not reentrant. It will happily create duplicate window actions to set as the rule's action_id. Given that the UI now allows to call subscribe on subscribed records, can you fix this?