Clean-up SyncWithWallets/SyncTransaction

- replace g_signals.SyncTransaction with SyncWithWallets for consistency
- remove SyncTransaction from ConnectBlock. ConnectBlock is called from ConnectTip, we already sync there, no need to sync the txs twice.
- remove SyncWithWallets from sendrawtransaction. We call SyncWithWallets in AcceptToMemoryPool.

I tested sendrawtransaction, tx showed up in the GUI. Tested sending a tx, then start new wallet and wait for tx from block, tx showed up in the GUI.