fix(ci): Failures on Main: Compiler GPU Tests, Tokenizer, and JsonArgparse Issues

[bhimrazy]

What does this pr do ?

This PR addresses and stabilizes multiple CI failures currently affecting the main branch.

Key Fixes

• Partial fix for jsonargparse==4.42.0 causing test_config_help failure #2150 — temporary fix for errors caused by jsonargparse.

• Fix compiler GPU tests:

  • Use PyTorch 2.8.0 image to resolve NVFuser-related failures.
  • Fix Thunder’s test_networks.py by aligning with its dependency pin transformers==4.52.4 (see: https://github.com/Lightning-AI/lightning-thunder/blob/main/requirements/test.txt).
  • Add fixture turn_off_tf32_and_set_seed, required by Thunder’s network tests.

• Fix tokenizer tests (test_tokenizer_against_hf) failing due to 429 Too Many Requests by introducing reruns with delay for stability.

• Add TORCH_URL to download cpu based packages for cpu tests which should resolve any space related issues (eg: https://github.com/Lightning-AI/litgpt/actions/runs/19007773138/job/54284274578?pr=2149)

closes #2143

Notes

All GPU tests are now passing.
Only a minor issue remains to be addressed in the CPU test suite.

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[bhimrazy]

Finally both gpu tests have passed.

[Borda]

@lantiga needs to update the branch protection setting and replace Azure-gpu by lit-gpu