## Issue Addressed
Following the conversation on https://github.com/libp2p/rust-libp2p/pull/3666 the changes introduced in this PR will allow us to give more insights if the bandwidth limitations happen at the transport level, namely if quic helps vs yamux and it's [window size limitation](https://github.com/libp2p/rust-yamux/issues/162) or if the bottleneck is at the gossipsub level.
## Proposed Changes
introduce new quic and tcp bandwidth metric gauges.
cc @mxinden (turned out to be easier, Thomas gave me a hint)
f06391717c