Add explicit permissions to CI workflow

[yugannkt]

Description

This PR adds explicit permissions to the CI workflow file (.github/workflows/CI.yml) to follow security best practices and the principle of least privilege.

Changes

• Added workflow-level default permissions with contents: read as the minimum baseline
• Added job-level permissions for each job with only the permissions they require:
  • build: contents: read, actions: write, security-events: write
    • Needs to checkout code, upload artifacts, and perform CodeQL security analysis
  • upload-event-file: contents: read, actions: write
    • Needs to upload the GitHub event file as an artifact
  • build-for-e2e-test: contents: read, actions: write
    • Needs to build and upload binary artifacts for different platforms
  • e2e-test: contents: read, actions: write, checks: write
    • Needs to download artifacts, upload test logs, and publish test results
  • publish: contents: write
    • Needs to create releases and commit release notes back to the repository

Fixes #1457

• Did you write/update appropriate tests
• Release notes updated (if appropriate)
• Appropriate logging output
• Issue linked
• Docs updated (or issue created)
• New package licenses are added to ThirdPartyNotices.txt (if applicable)

[github-actions]

Unit Test Results

  1 files    1 suites   10m 25s ⏱️
960 tests 960 ✅ 0 💤 0 ❌
961 runs  961 ✅ 0 💤 0 ❌

Results for commit 83f609a.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
ado2gh	72%	70%	712	➖
Octoshift	83%	72%	1739	✔
bbs2gh	83%	78%	663	✔
gei	81%	72%	574	✔
Summary	81% (7738 / 9604)	73% (1840 / 2521)	3688	✔