`banlist.dat` was introduced in https://github.com/bitcoin/bitcoin/pull/6310, storing nodes that were automatically banned (due to exceeding the misbehavior threshold) and manually banned (through the `setban` RPC).

Automatic bans were removed in https://github.com/bitcoin/bitcoin/pull/19219 and replaced with a discouragement filter. That filter is not saved to disk/persisted over shutdown/startup. The `banlist.dat` therefore now only contains addresses that have been banned through the `setban` rpc.

Since https://github.com/bitcoin/bitcoin/pull/15935, we have a specific file for configuration that is updated through the RPC and persisted over shutdown/startup, namely `settings.json`. We should therefore move the manual ban configuration from `banlist.dat` to `settings.json`. Doing so has a couple of benefits:

- `settings.json` is human readable and easily analyzable by any json parser.
- we wouldn't need to maintain custom [de]serialization code for the `banlist.dat` file.

`banlist.dat` is expected to be fairly small and infrequently updated, so disk space/performance are not huge concerns.
SetMockTime(nStartTime+21*60);
    {
        LOCK(dummyNode1.cs_sendProcessing);
        BOOST_CHECK(peerLogic->SendMessages(&dummyNode1)); 
    }
    {
        LOCK(dummyNode1.cs_vSend);
        BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
    }
    
    SetMockTime(nStartTime+24*60);
    {
        LOCK(dummyNode1.cs_sendProcessing);
        BOOST_CHECK(peerLogic->SendMessages(&dummyNode1)); 
    }
    BOOST_CHECK(dummyNode1.fDisconnect == true);
    peerLogic->FinalizeNode(dummyNode1);
}
static void AddRandomOutboundPeer(std::vector<CNode*>& vNodes, PeerManager& peerLogic, ConnmanTestMsg& connman)
{
    CAddress addr(ip(g_insecure_rand_ctx.randbits(32)), NODE_NONE);
    vNodes.emplace_back(new CNode(id++, ServiceFlags(NODE_NETWORK | NODE_WITNESS), INVALID_SOCKET, addr,  0,  0, CAddress(),  "", ConnectionType::OUTBOUND_FULL_RELAY,  false));
    CNode &node = *vNodes.back();
    node.SetCommonVersion(PROTOCOL_VERSION);
    peerLogic.InitializeNode(&node);
    node.fSuccessfullyConnected = true;
    connman.AddTestNode(node);
}
BOOST_AUTO_TEST_CASE(stale_tip_peer_management)