[Dev] Fix ep overlap missing final layernorm

[Wohox]

What does this PR do ?

This PR fixes the missing final layernorm bug when below conditions are met:

• enable ep overlap with VPP
• number of mtp layers is 0
• last VPP rank only contain LM loss
  For example: PP layout E(tt|)*3L

Note: Main branch MR: #2136

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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Pre-checks

• I want this PR in a versioned release and have added the appropriate Milestone (e.g., Core 0.8)
• 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
• I have run the autoformatter.sh on my PR

Code review

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For MRs into `main` branch

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Final Review might get declined if these requirements are not fulfilled.

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The proposed review process for `dev` branch is under active discussion.

MRs are mergable after one approval by either eharper@nvidia.com or zijiey@nvidia.com.

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[Wohox]

cc @hxbai

[Wohox]

/ok to test 65c6919

[BestJuly]

LGTM. Please fix the linting and the copyright check.

[Wohox]

/ok to test 3e78312

[Wohox]

/ok to test ba38e01

[Wohox]

/ok to test 66658e8