channeldb: replace fetch channels booleans with optional filters

This changes replaces the pending an waiting booleans in fetchChannels
with optional filters which can be more flexibly used. This change
allows filtering of channels without having to reason about the matrix
of possible boolean combinations. A test is added to ensure that the
combinations of these filters act as expected.

channeldb/channel_test.go

@@ -187,6 +187,13 @@ func fundingPointOption(chanPoint wire.OutPoint) testChannelOption {
 	}
 }
 
+// channelIDOption is an option which sets the short channel ID of the channel.
+var channelIDOption = func(chanID lnwire.ShortChannelID) testChannelOption {
+	return func(params *testChannelParams) {
+		params.channel.ShortChannelID = chanID
+	}
+}
+
 // createTestChannel writes a test channel to the database. It takes a set of
 // functional options which can be used to overwrite the default of creating
 // a pending channel that was broadcast at height 100.