protocols/gossipsub: Revert back to wasm_timer for interval

[AgeManning]

As described in #2497 the current implementation for Interval in gossipsub can cause some serious issues with how gossipsub functions.

The heartbeat interval can grow unbounded, which unbounds the memory cache, exploding RAM and causes messages to be gossiped much later than they should be which can lead to very old messages being re-propagated on networks.

This PR reverts the Interval implementation back to wasm_timer. This should be sufficient to get gossipsub to work as expected however it was noted that this is not as performant as a straight tokio::time::Interval. A future PR should be made that ports the interval to be tokio agnostic, yet equally performant and compatible with WASM on NodeJS.

[mxinden]

Looks good to me. Thanks for reverting. Could you include a changelog entry as well?

Also I think this needs to use wasm_timer::Instant instead of instant::Instant.

//CC @wngr

[divagant-martian]

Also I think this needs to use wasm_timer::Instant instead of instant::Instant.

#2245 made the ProtocolsHandler trait dependent on instant

[divagant-martian]

I've removed support for gossipsub in the wasm targets. It's sad since before #2245 there was support for the other two targets, but the instant::Instant vs wasm_timer::Instant incompatibility makes this the only reasonable solution that I can see for now.

[divagant-martian]

Following @mxinden suggestion, Gossipsub should now be removed only in the wasm32-unknown-unknown target. I'm using cargo tree to verify this:

> cargo tree -e features --target=wasm32-unknown-unknown | rg gossipsub
# empty
> cargo tree -e features --target=wasm32-wasi | rg gossipsub
#├── libp2p-gossipsub feature "default"
#│   └── libp2p-gossipsub v0.36.0 (/home/me/rust-libp2p/protocols/gossipsub)
#│       ├── libp2p-gossipsub feature "default" (*) # libp2p-metrics dep
> cargo tree -e features --target=wasm32-unknown-emscripten | rg gossipsub
#├── libp2p-gossipsub feature "default"
#│   └── libp2p-gossipsub v0.36.0 (/home/me/rust-libp2p/protocols/gossipsub)
#│       ├── libp2p-gossipsub feature "default" (*) # libp2p-metrics dep

[mxinden]

Thanks @divagant-martian and @AgeManning!