[network] Consolidate repeated code in ConnMgr tests
[network] Consolidate repeated code in ConnMgr tests

There was a ton of differing and repeated code for setup and other things
in the conn mgr.  This attempts to rid the code of some of the old
paradigms prior to the `Peer` object

Closes: #7555

aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra