Merge CI checks into VMSS A job

[achamayou]

Two changes from #7417:

1. Merge CI checks in, to cut down what otherwise adds ~5 minutes of startup latency to most CI runs
2. Rename jobs to A and B, they are packed for latency, not necessarily by theme. The contents are still in comment.

[Copilot]

Pull Request Overview

This PR consolidates CI workflows by removing a separate pre-check job and integrating its functionality into the main build jobs. The changes streamline the CI pipeline by consolidating dependency installation and removing serial job dependencies.

• Removed the separate checks job and integrated CI checks into the first virtual build job
• Moved package installations (tar, npm, build-essential) from the workflow to the setup-dev.sh script
• Removed needs: checks dependencies from SNP jobs to enable parallel execution

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
scripts/setup-dev.sh	Added tar, npm, and build-essential packages; removed vim from installation list
.github/workflows/ci.yml	Removed separate checks job, integrated checks into vmss-virtual-a job, removed job dependencies to enable parallelization