[dynamo] utility to generate bytecode from template function (#127359)

This will be helpful in reducing some of the hardcoded and python-version-dependent bytecode generation in various places in dynamo - e.g. resume function generation and object reconstruction.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/127359
Approved by: https://github.com/jansel
ghstack dependencies: #127329

torch/_dynamo/testing.py

@@ -343,6 +343,12 @@ def skipIfNotPy311(fn):
     return unittest.skip(fn)
 
 
+def skipIfNotPy312(fn):
+    if sys.version_info >= (3, 12):
+        return fn
+    return unittest.skip(fn)
+
+
 def xfailIfPy312(fn):
     if sys.version_info >= (3, 12):
         return unittest.expectedFailure(fn)