Highlight a selected plugin's masters and plugins that depend on it

[Infernio]

Has come up a few times on Discord and recently here (#400). Idea would be exactly what the title says - if you select a plugin, all masters of the plugin and all plugins that have the plugin as a master are highlighted in the mods list. I'd imagine the best way to do this would be to show a different, muted background color. There should be an option to turn it off, and obviously the colors should be configurable.