channeldb: BigSize migration, store zero-conf, scid-alias bits

This introduces a BigSize migration that is used to expand the width
of the ChannelStatus and ChannelType fields. Three channel "types"
are added - ZeroConfBit, ScidAliasChanBit, and ScidAliasFeatureBit.
ScidAliasChanBit denotes that the scid-alias channel type was
negotiated for the channel. ScidAliasFeatureBit denotes that the
scid-alias feature bit was negotiated during the *lifetime* of the
channel. Several helper functions on the OpenChannel struct are
exposed to aid callers from different packages.

The RefreshShortChanID has been renamed to Refresh.

A new function BroadcastHeight is used to guard access to the
mutable FundingBroadcastHeight member. This prevents data races.

channeldb/channel_test.go

@@ -1148,10 +1148,10 @@ func TestFetchWaitingCloseChannels(t *testing.T) {
 	}
 }
 
-// TestRefreshShortChanID asserts that RefreshShortChanID updates the in-memory
-// state of another OpenChannel to reflect a preceding call to MarkOpen on a
-// different OpenChannel.
-func TestRefreshShortChanID(t *testing.T) {
+// TestRefresh asserts that Refresh updates the in-memory state of another
+// OpenChannel to reflect a preceding call to MarkOpen on a different
+// OpenChannel.
+func TestRefresh(t *testing.T) {
 	t.Parallel()
 
 	fullDB, cleanUp, err := MakeTestDB()
@@ -1209,8 +1209,8 @@ func TestRefreshShortChanID(t *testing.T) {
 			state.Packager.(*ChannelPackager).source)
 	}
 
-	// Now, refresh the short channel ID of the pending channel.
-	err = pendingChannel.RefreshShortChanID()
+	// Now, refresh the state of the pending channel.
+	err = pendingChannel.Refresh()
 	require.NoError(t, err, "unable to refresh short_chan_id")
 
 	// This should result in both OpenChannel's now having the same