Issue-88098: extract utils from check labels (#94597)
Fixes #88098
This is a mirror of the same PR (https://github.com/Goldspear/pytorch/pull/2) that has been reviewed in my fork (due to it's a stacked PR).
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## Context
This is the 2nd of the 3 PRs to address issue-88098.
## What Changed
1. Extract comment related utils from trymerge.py to github_utils.py
2. Extract label related utils from trymerge.py and check_labels.py to label_utils.py
## Tests
* pytorch-dummy repo [trymerge run ](https://github.com/Goldspear/pytorch-dummy/actions/runs/4118944174)merged the test PR [OK](https://github.com/Goldspear/pytorch-dummy/pull/2).
## Note to Reviewers
Due to higher degree of complexity involved to extract GitHubPR class, it's worth having a separate issue to handle that part of refactoring. This issue only focusing on refactoring where necessary to ship the functional diff.
* 1st PR: https://github.com/pytorch/pytorch/pull/94179
* 2nd PR: this one
* 3rd PR: https://github.com/Goldspear/pytorch/pull/3
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94597
Approved by: https://github.com/ZainRizvi
