Update on "[AOTI] Refactor some fallback op util functions"

Summary: Move some util functions for cpp kernel naming and missing arg filling from FallbackKernel to ExternKernel, since they are useful for ExternKernel in general.

cc voznesenskym penguinwu EikanWang jgong5 Guobing-Chen XiaobingSuper zhuhaozhe blzheng wenzhe-nrv jiayisunx peterbell10 ipiszy yf225 chenyang78 kadeng muchulee8 ColinPeppler amjames chauhang

[ghstack-poisoned]

torch/_inductor/codegen/cpp_wrapper_cpu.py

@@ -1120,7 +1120,7 @@ def g(args):
         )
 
     def get_c_shim_func_name(self, kernel):
-        if not config.abi_compatible:
+        if not config.abi_compatible or kernel.startswith("aoti_torch_"):
             return kernel
 
         assert "::" in kernel, "Cpp kernel name: " + kernel + " does not contain '::'"