For performance, use a plugin we're already using
More reliable behavior for network activating a plugin

* If the plugin is already active, allow it to be network-activated.
* If the plugin is already network-active, don't change status.
Drop tag used for local dev
Drop tests we no longer need
More consistent behavior for plugin deactivation

* Network active plugins must be deactivated with `--network` flag
* Throw a warning when an inactive plugin is attempted to be deactivated
* Active plugins must be deactivated before network activating
Update plugin fetcher to match on full path

WordPress stores dirname/filename.php in the database, so this is a
valid name to use
Drop unnecessary abstraction

We're dropping duplicate code, and reusing our status checking logic
Merge pull request #1578 from wp-cli/1556-network-activate-plugin

More consistent behavior for plugin (de)activation