[Dev][Draft] fix(moe): Support HybridEP and reduce memory overhead for 1F1B A2A overlap

[lhb8125]

What does this PR do ?

PR for main

• replace enable_deepep with use_flex_dispatcher so that deepep and hybridep will be treated in the same way in 1f1b a2a overlap;
• add some deconstructors in 1f1b a2a overlap to release the references to tensors, which helps to reduce the memory overhead;

:warning: 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
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• [ ] I have added relevant documentation
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[yanring]

Thanks for the PR. Please mark the title with [Dev] fix(moe): xxx and label this PR with module:moe and dev.

[lhb8125]

/ok to test 32fc988

[yanring]

/ok to test 6102cc5

[yanring]

/ok to test d29b634

[lhb8125]

The UT failed for some reasons. Will reopen the PR after the issue is fixed.

[lhb8125]

/ok to test e0e6da1

[lhb8125]

/ok to test 04199ce

[lhb8125]

/ok to test e9e662b

[lhb8125]

/ok to test fe05568

[lhb8125]

/ok to test 776d224

[lhb8125]

/ok to test 487eea9

[lhb8125]

@yanring @Victarry Could you give a final review of this PR? We did some modifications after the previous changes.

[lhb8125]

/ok to test c568c37

[yanring]

@lhb8125 could you fix the api checks? https://github.com/NVIDIA/Megatron-LM/blob/main/docs/api-backwards-compatibility-check.md

[lhb8125]

/ok to test 36648e3

[lhb8125]

/ok to test 0708cc1

[lhb8125]

/ok to test 2cfaec1

[lhb8125]

/ok to test 0f8663b

[lhb8125]

/ok to test 97de523

[lhb8125]

/ok to test 12a2a22