Reduce MAX_PEER_TX_ANNOUNCEMENTS for non-PF_RELAY peers

Maintaining up to 100000 INVs per peer is excessive, as that is far more
than fits in a typical mempool.

Also disable the "overload" penalty for PF_RELAY peers.

src/net_permissions.h

@@ -19,6 +19,7 @@ enum NetPermissionFlags {
     // Can query bloomfilter even if -peerbloomfilters is false
     PF_BLOOMFILTER = (1U << 1),
     // Relay and accept transactions from this peer, even if -blocksonly is true
+    // This peer is also not subject to limits on how many transaction INVs are tracked
     PF_RELAY = (1U << 3),
     // Always relay transactions from this peer, even if already in mempool
     // Keep parameter interaction: forcerelay implies relay