update openrc to persistence mixin

[h00die]

Pulls out openrc from the init persistence module and adds new persistence mixin. Part of #20374

Verification

• Start msfconsole
• exploit the box somehow (ssh_login for instance)
• use exploit/linux/persistence/init_openrc
• set SESSION <id>
• exploit
• Verify persistence is created, and you get a new session if apt is run
• Verify cleanup works
• Document is updated and correct

[msutovsky-r7]

Is this new module? Should we add module tag instead?

[h00die]

Nope, the service_persistence.rb module was just WAY too complex trying to handle services between all the available init systems, so i divided it out. This init system per module makes much more sense when persistence_suggester lands as well.