Add local task plugin deriver to use YAML discovery for static definitions

Currently, you have to implement an empty class for any local task plugin. This is a bit weird, you are then just using the empty class for the annotation. It makes sense, similar to routes, to have YAML discovery for these, then static local tasks just get added into a $module.localtasks.yml file. This seems like better UX, as people can then actually create a plugin class for dynamic local tasks.

Related Issues:

#2050227: Add local action plugin deriver to use YAML discovery for static definitions