Core v28 support is broken

[tcharding]

The node crate has a unit test test_multi_p2p that does not work for Bitcoin Core v28. I think the reason is something to do with how port binding was changed in this release. See P2P and Network Changes section of the release notes.

To close this issue remove the feature guard on the test_multi_p2p unit test.

[tcharding]

FTR this issue is also documented in the code

    // In v28:
    //
    // > Bitcoin Core will now fail to start up if any of its P2P binds fail, rather than the
    // > previous behaviour where it would only abort startup if all P2P binds had failed.
    //
    // ref: https://bitcoincore.org/en/releases/28.0/
    // ref: https://github.com/bitcoin/bitcoin/pull/22729
    //
    // I tried various things to stop bitcoind attempting to bind on 18445 but could get nothing to work.
    //
    // - Tried using arg `-torcontrol=0`.
    // - Tried using arg `-listenonion=0`.
    // - Tried using arg `-bind={available_port}`.
    // - Tried using arg `-bind={available_port}=onion`.
    // - Tried using both the two bind args above together.
    #[cfg(not(feature = "28_0"))]
    fn test_multi_p2p() {

[tcharding]

Suggested fix here: RCasatta/electrsd#89 (comment)