Resource Manager: Remove ResourceMgr.Limits configuration from Kubo and use the default libp2p JSON file for it

[ajnavarro]

Resource Manager config is really useful when you want to configure every aspect of your kubo node, but it is very complex for the average user.

We should remove .Limits field from our configuration, only allowing us to change MaxMemory and MaxFileDescriptors as configurable parameters for RM.

If some experienced user wants to modify any RM low-level parameter, they can still do it by creating a limits.json file near by kubo config that will be read using default libp2p functions:

https://github.com/libp2p/go-libp2p/blob/97607949208fc95bea759eeaa88db3ad2c86bf38/p2p/host/resource-manager/limit.go#L59

We also need to make a decision on how we handle legacy Swarm.ResourceMgr.Limits configuration.

[BigLep]

On the topic of Swarm.ResourceMgr.Limits configuration, my initial vote is that we don't migrate it and use this as an opportunity to have users reset and figure out what they actually need.

[lidel]

+1 – no migration, most users won't have custom Swarm.ResourceMgr.Limits.

If someone set custom limits, we should error after update to new Kubo, asking them to remove Swarm.ResourceMgr.Limits from config, and try defaults (and if the need custom limits, link to go-libp2p docs around limits.json)

Prior art (Fatal will log error end shut down the daemon) :

kubo/cmd/ipfs/daemon.go

Line 458 in ed4d6b7

log.Fatal("Private network does not work with Routing.Type=auto. Update your config to Routing.Type=dht (or none, and do manual peering)")