[Dev] Reduce Overhead in Timers

[yaox12]

What does this PR do ?

PR to the main branch: #2210

Update: when there're no timers to log (e.g., log_level=0), only ~0.02ms overhead.

Previously, timers.log takes ~5ms, where a lot of PyTorch ops are invoked.

Now, it's reduced to ～0.44 ms.

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.

(Step 3): Final Review

1. Add Final Review label
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(Optional Step 4): Cherry-pick into release branch

If this PR also needs to be merged into core_r* release branches, after this PR has been merged, select Cherry-pick to open a new PR into the release branch.

For MRs into `dev` branch

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.

Merging your PR

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[yaox12]

Grouped by the levels at which they're created.

[FDecaYed]

LG

[yaox12]

/ok to test 970f01b

[yaox12]

/ok to test 6fa642c

[yaox12]

/ok to test 9a09a00