Stop storing references to bound methods via tf.function (#24146)

* Stop storing references to bound methods in tf.functions

* Remove the gc.collect calls now that we resolved the underlying problem

* Remove the default signature from model.serving entirely, big cleanup

* Remove _prune_signature as self.input_signature can prune itself

* Restore serving docstring

* Update int support test to check the input signature

* Make sure other tests also use model.input_signature and not serving.input_signature

* Restore _prune_signature

* Remove the doctest GC now it's no longer needed

* Correct core tests to use the pruned sig

* order lines correctly in core tests

* Add eager_serving back with a deprecation warning

src/transformers/testing_utils.py

@@ -1882,13 +1882,6 @@ def preprocess_string(string, skip_cuda_tests):
     if not is_cuda_found:
         modified_string = "".join(codeblocks)
 
-        if ">>>" in modified_string:
-            lines = modified_string.split("\n")
-            indent = len(lines[-1]) - len(lines[-1].lstrip())
-
-            cleanup = ">>> import gc; gc.collect()  # doctest: +IGNORE_RESULT"
-            modified_string += "\n" + " " * indent + cleanup
-
     return modified_string