gen_static_metadata.py would generate .cc now. Also fixed asan build failures

src/core/ext/transport/chttp2/transport/flow_control.cc

@@ -86,7 +86,7 @@ static char* fmt_uint32_diff_str(uint32_t old_val, uint32_t new_val) {
 
 static void posttrace(shadow_flow_control* shadow_fc,
                       grpc_chttp2_transport_flowctl* tfc,
-                      grpc_chttp2_stream_flowctl* sfc, char* reason) {
+                      grpc_chttp2_stream_flowctl* sfc, const char* reason) {
   uint32_t acked_local_window =
       tfc->t->settings[GRPC_SENT_SETTINGS]
                       [GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE];
@@ -128,7 +128,7 @@ static void posttrace(shadow_flow_control* shadow_fc,
   gpr_free(saw_str);
 }
 
-static char* urgency_to_string(grpc_chttp2_flowctl_urgency urgency) {
+static const char* urgency_to_string(grpc_chttp2_flowctl_urgency urgency) {
   switch (urgency) {
     case GRPC_CHTTP2_FLOWCTL_NO_ACTION_NEEDED:
       return "no action";

tools/codegen/core/gen_static_metadata.py

@@ -304,7 +304,7 @@ else:
   C = open(
       os.path.join(
           os.path.dirname(sys.argv[0]),
-          '../../../src/core/lib/transport/static_metadata.c'), 'w')
+          '../../../src/core/lib/transport/static_metadata.cc'), 'w')
   D = open(
       os.path.join(
           os.path.dirname(sys.argv[0]),