fundingmanager: Update tests for funding manager persistence

This commit adds the FundingManagerPersistence test to ensure that the
funding process completes as expected when nodes shutdown after the the
funding transaction has been broadcast. Note that the final parts of
several wallet tests have been removed, as functionality has been moved
to the Funding Manager and should now be tested there.

lnwallet/wallet.go

@@ -1189,6 +1189,10 @@ func (l *LightningWallet) handleSingleFunderSigs(req *addSingleFunderSigsMsg) {
 
 	req.completeChan <- pendingReservation.partialState
 	req.err <- nil
+
+	l.limboMtx.Lock()
+	delete(l.fundingLimbo, req.pendingFundingID)
+	l.limboMtx.Unlock()
 }
 
 // selectCoinsAndChange performs coin selection in order to obtain witness