chore: Google Style Guide Shellcheck Compliance

[mohitsaxenaknoldus]

What problem are you facing?

While working on some of the issues, I noticed we don't follow Google Style Guide. Shellcheck compliance was there but not in all places. We should implement these to have a cleaner and more easily maintainable code in the long run.

I can raise a PR for this if you'd like.

How could pre-commit-terraform help solve your problem?

[yermulnik]

May worth sync'ing with @MaxymVlasov on this I think.

[MaxymVlasov]

Feel free to do refactoring, just by small butches (no more than 1-2 days in the row), and mention here when you start to do it.
Have no ongoing refactor work on my side for now.

[github-actions]

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[MaxymVlasov]

Depends on #303