Auto-detect feature layer for Pytorch models

[goodsong81]

[Changes]

• [x] Feature layer auto detection (by lazy one-time forward hook)
  • CNNs: the last layer which outputs 4D maps w/ spatial dimension
  • ViTs: the N-last LayerNorm layer (Different from OV logic as there is no explicit Add module just before the LayerNorm in Pytorch models)

[Future works]

• [ ] Refactoring + torch optional install
• [ ] Documentation + example
• [ ] Functional tests

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.07843% with 2 lines in your changes missing coverage. Please review.

Project coverage is 94.23%. Comparing base (8b0ddf9) to head (6617ccb). Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
openvino_xai/methods/white_box/torch.py	96.07%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #64 +/- ## =========================================== + Coverage 94.16% 94.23% +0.07% =========================================== Files 27 27 Lines 1817 1857 +40 =========================================== + Hits 1711 1750 +39 - Misses 106 107 +1 ``` | [Flag](https://app.codecov.io/gh/openvinotoolkit/openvino_xai/pull/64/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | Coverage Δ | | |---|---|---| | [dev-py310](https://app.codecov.io/gh/openvinotoolkit/openvino_xai/pull/64/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit) | `94.23% <96.07%> (+0.07%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openvinotoolkit#carryforward-flags-in-the-pull-request-comment) to find out more.

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