feat/ci: use commit hash for actions, add arm64 support to test workflow

[kbdharun]

Changes

• This PR switches all version based rewritable action tags to use commit hashes instead.
• Dependabot frequency for GitHub action update check has been changed to “weekly” to incorporate point releases quickly (since we are using hash based approach from now).
• Add GitHub's free partner arm runner (currently in public preview) to build job in test workflow to test the code changes in arm64 too along with amd64.
• I have renamed snapcore/action-build to canonical/action-build since the latter one is the base repo and snapcore one is a fork.

[Managor]

I have no experience with these systems, thus my approval is very useless. I glanced at the changes and they're looked probably ok.

[owenvoke]

LGTM.

One query, I assume Dependabot won't update the version comments next to the commits? 🤔 If not, then they will probably get outdated pretty quickly unless we manually update the comments for each Dependabot PR.

[kbdharun]

One query, I assume Dependabot won't update the version comments next to the commits? 🤔 If not, then they will probably get outdated pretty quickly unless we manually update the comments for each Dependabot PR.

Actually Dependabot takes care of updating the version comments too, checkout https://github.blog/changelog/2022-10-31-dependabot-now-updates-comments-in-github-actions-workflows-referencing-action-versions/ while it's not clearly mentioned in docs, I have seen it working in other projects using commit SHA for actions.

Checkout tldr-pages/tldr#15947 for more information.

[owenvoke]

Nice! I didn't know that, and that's pretty cool. 🙌🏻

[kbdharun]

Implemented ARM support for building snaps too.

I will update the build-snap job to be dependent on build job's completion so that if something in a PR is broken and is reflected in the build then no need to build snap to confirm the same (this will save a few minutes from workflow runs assisting in faster debugging/review process).

[kbdharun]

Done, implemented it. Now the PR is GTG.

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Adding some screenshots for future reference:-

Before:

After: