[torch][ao] Fix module name filter for pytorch2 quantization for underscores (#119344)
Summary:
There was a bug in the module name filter for modules that had an underscore
already in them, as it was replaced with a "dot" notation.
This is because it was thought that underscores always meant a module separator,
but this isn't the case for modules whose name contains an underscore.
Test Plan:
Added a unit test. Before this change, that test failed (due to applying the wrong
qscheme). Now it passes.
Differential Revision: D53502771
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119344
Approved by: https://github.com/jerryzh168
