Move preloaded interconnect to the header file

`interconnect` is expected to preload if the macro option
ENABLE_PRELOAD_IC_MODULE is set. The header file
`process_shared_preload_libraries.h` is kept to save all
builtin shared preloaded libraries.

This commit defines the `interconnect` preload in
`process_shared_preload_libraries.h` to minimize code
diverge.

src/backend/utils/init/miscinit.c

@@ -1891,7 +1891,7 @@ process_shared_preload_libraries(void)
 {
 	process_shared_preload_libraries_in_progress = true;
 
-	char* libraries = expand_shared_preload_libraries_string();
+	char *libraries = expand_shared_preload_libraries_string();
 	load_libraries(libraries,
 				   "shared_preload_libraries",
 				   false);
@@ -1900,12 +1900,6 @@ process_shared_preload_libraries(void)
 		pfree(libraries);
 	}
 
-#ifdef ENABLE_PRELOAD_IC_MODULE
-	load_libraries("interconnect",
-				   "preload interconnect module",
-				   false);
-#endif
-
 	process_shared_preload_libraries_in_progress = false;
 	process_shared_preload_libraries_done = true;
 }

src/include/utils/process_shared_preload_libraries.h

@@ -0,0 +1,3 @@
+#ifdef ENABLE_PRELOAD_IC_MODULE
+  "interconnect",
+#endif