channeldb+graphdb: init graph DB outside of channel db

We also now use the graph DB's own optional functions. An instance of
the graph is currently still passed to the channeldb's
`CreateWithBackend` function. This will be removed in a later commit
once the two have been completely disjoint.

graph/db/graph_test.go

@@ -79,11 +79,7 @@ func MakeTestGraph(t testing.TB, modifiers ...OptionModifier) (*ChannelGraph, er
 		return nil, err
 	}
 
-	graph, err := NewChannelGraph(
-		backend, opts.RejectCacheSize, opts.ChannelCacheSize,
-		opts.BatchCommitInterval, opts.PreAllocCacheNumNodes,
-		true, false,
-	)
+	graph, err := NewChannelGraph(backend)
 	if err != nil {
 		backendCleanup()
 		return nil, err
@@ -4016,12 +4012,7 @@ func TestGraphLoading(t *testing.T) {
 	defer backend.Close()
 	defer backendCleanup()
 
-	opts := DefaultOptions()
-	graph, err := NewChannelGraph(
-		backend, opts.RejectCacheSize, opts.ChannelCacheSize,
-		opts.BatchCommitInterval, opts.PreAllocCacheNumNodes,
-		true, false,
-	)
+	graph, err := NewChannelGraph(backend)
 	require.NoError(t, err)
 
 	// Populate the graph with test data.
@@ -4031,11 +4022,7 @@ func TestGraphLoading(t *testing.T) {
 
 	// Recreate the graph. This should cause the graph cache to be
 	// populated.
-	graphReloaded, err := NewChannelGraph(
-		backend, opts.RejectCacheSize, opts.ChannelCacheSize,
-		opts.BatchCommitInterval, opts.PreAllocCacheNumNodes,
-		true, false,
-	)
+	graphReloaded, err := NewChannelGraph(backend)
 	require.NoError(t, err)
 
 	// Assert that the cache content is identical.