Enable specifying infinite limits with a more "intuitive" magic number like -1

[BigLep]

I know programmatically one can use inifiteLimits. In the Kubo case where users are defining their limits via config/JSON, it would be useful to have another value that denotes infinity like "-1". Certainly Kubo can create its own infinity value but we'd need to do the conversion when setting up the resource manager and reading limits back out from it. I assume this will be pretty common for other applications building on top of go-libp2p which is what I'm proposing putting it into go-libp2p itself.

Context: this came as part of handling user reports after enabling the resource manager by default in Kubo: ipfs/kubo#9442

[marten-seemann]

This should be covered by #2000. The magic number is not -1, but "unlimited" (in the JSON serialization).