[pruning][core][feature] Align BaseStructuredPruner with existing pruning flow (#88436)
Summary:
This PR aligns the "eager" mode of the structured pruning flow with the existing unstructured pruning flow.
The base pruner has been moved from and has been renamed from BasePruner to BaseStructuredPruner
`torch/ao/pruning/_experimental/pruner/base_pruner.py -> /torch/ao/pruning/_experimental/pruner/base_structured_pruner.py`
Support for pruning batchnorm modules in the config have been removed, so now the structured pruning code can use more of the BaseSparsifier logic and we don't need to override as many functions.
Since we aim to only support a single flow, we have only updated ZeroesParametrizations (FakeStructuredSparsity) and BiasHook.
The parameterizations have also been rewritten to use a bool mask tensor for keeping track of pruned rows, instead of using sets before.
This better aligns structured and unstructured sparsity.
The BaseStructuredSparsifier tests have also been updated to reflect the above changes. I also removed `squash_mask` tests because they were breaking CI and `squash_mask` is no longer used.
We will migrate the structured pruning code out of this folder in a later PR.
Test Plan:
```
python test/test_ao_sparsity -- TestBaseStructuredPruner
```
Reviewers:
z-a-f vkuzo
Subscribers:
Tasks:
Tags:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88436
Approved by: https://github.com/vkuzo
