fix(tests): flaky timeout to wait for peer-exchange

[Danish Arora]

This is a change request

Problem

For our compliance test:

js-waku/packages/tests/tests/peer-exchange/compliance.spec.ts

Lines 51 to 54 in 6f188ef

 // we do this because we want peer-exchange discovery to get initialised before we dial the peer which contains info about the other peer 
 setTimeout(() => { 
   void waku.libp2p.dialProtocol(nwaku2Ma, PeerExchangeCodec); 
 }, 1000); 

, we seem to wait 1000ms/1s, to ensure peer-exchange is mounted on the js-waku node.

This is quite hacky, and seems to introduce some race conditions as brought up by @gabrielmer.

Proposed Solutions

Use a more predictable logic that waits for peer-exchange to be mounted.
Eg: peerExchange.isMounted/peerExchange.on("mounted")