Add fidl_binding_deps support from the Fuchsia SDK json files (#813)

The GN rules that parse the SDK json files previously only supported the
`fidl_deps` field for determining which fidl dependencies to depend on.
This change adds support for the newer `fidl_binding_deps` field, which
contains information about what flavor of bindings are needed (hlcpp vs
natural). Since our fidl GN targets always generate both hlcpp and
natural bindings, we don't need to check the binding_type in the json
file.

build/fuchsia/sdk.gni

@@ -224,6 +224,14 @@ template("_fuchsia_cc_source_library") {
     _deps += [ "../fidl:$dep" ]
   }
 
+  foreach(binding_dep, meta_json.fidl_binding_deps) {
+    # No need to check "binding_deps.binding_type" because we always
+    # generate both hlcpp and natural bindings.
+    foreach(dep, binding_dep.deps) {
+      _deps += [ "../fidl:$dep" ]
+    }
+  }
+
   source_set(target_name) {
     output_name = _output_name
     public = _public_headers