ci: migrate PR checks to GitHub Actions (#4004)

* Initial plan

* feat: add GitHub Actions PR workflow mirroring Azure Pipelines PR checks

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* fix: add explicit permissions to PR workflow to limit GITHUB_TOKEN scope

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* feat: add catch-all PR job that depends on all other checks

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* fix: resolve Windows SDK version mismatch on windows-latest runner

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* chore: update setup-toolchain to 5.0.14

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* fix: use Windows SDK 10.0.26100.0 (the only SDK available on windows-latest)

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* chore: delete old Azure Pipelines PR checks

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

* ci: run Android PR job on ubuntu-latest instead of macos-latest

Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Saadnajmi <6722175+Saadnajmi@users.noreply.github.com>

Author: Copilot