Laptop Mode

I want to run ipfs on my laptop *all the time*.
I would like to have a mode for ipfs that works essentially only on demand. Basically, I want no network activity unless I request something. When I request something, I want the activity to spin back up, fetch what I need, and then slow back down (perhaps after some cooldown).

This could be done a couple different ways, but I think the best way to move towards this would be to add a feature/service to libp2p that allows us to signal information about connections to the peers who we have those connections with. This is also needed for proper connection closing, so that we can signal to another peer that we want to close a connection with them. With this service, we could also signal that we want to *pause* a connection to a peer (essentially a soft restriction on forming new streams).