Add FP8 quantization test

[nikita-savelyevv]

What does this PR do?

Follow-up to #1100. Changes:

• Add a test for FP8 quantization of a language model through python API (similar to this one).
• Update dataset name check for full quantization case.
• Variables renaming in tests (besides FakeQuantize nodes there are FakeConvert nodes too).

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[AlexKoff88]

@KodiaqQ, please take a look as well

[echarlaix]

LGTM!