Fix CUDA RNG Tracker

[buptzyb]

What does this PR do ?

Dev PR #2640

1. Let RandomSTE use expert-parallel-rng instead of a private generator.
2. No matter saved checkpoint in normal rng or graphable rng format, loading to either format is allowed, with the newly added convert_cuda_rng_state() function.
3. Fix a bug that _get_all_rng_states() get tracker rng in graphable format, but the default cuda rng in normal format. Now we make them return in the same format. Same for _set_all_rng_states().
4. Fix a bug in nested fork with non-graphble rng - always use the latest state.
5. Capture graphs in rng context - same as how it works in TransformerBlock.
6. Add related unit tests.

⚠️ For major changes (either in lines of code or in its impact), please make sure to first share discuss a design-doc with the team.

Contribution process

flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
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[buptzyb]

/ok to test 5de42ca

[buptzyb]

/ok to test 3cb957f

[buptzyb]

/ok to test abfc1e6

[buptzyb]

/ok to test 62e1a28