CI: Add a bash linter to pre-submits

[mandre]

Add a new CI job that warns about shellcheck issues with severity error, and fix all such errors in existing bash files.

This should prevent errors such as the one fixed in https://github.com/k8snetworkplumbingwg/sriov-network-operator/pull/780 from entering the repo again.

[github-actions[bot]]

Thanks for your PR, To run vendors CIs, Maintainers can use one of:

• /test-all: To run all tests for all vendors.
• /test-e2e-all: To run all E2E tests for all vendors.

• /test-e2e-nvidia-all: To run all E2E tests for NVIDIA vendor.

  To skip the vendors CIs, Maintainers can use one of:

• /skip-all: To skip all tests for all vendors.
• /skip-e2e-all: To skip all E2E tests for all vendors.
• /skip-e2e-nvidia-all: To skip all E2E tests for NVIDIA vendor. Best regards.

[coveralls]

Pull Request Test Coverage Report for Build 11249043430

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 45.143%

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Totals
Change from base Build 11248365096:	0.02%
Covered Lines:	6659
Relevant Lines:	14751

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💛 - Coveralls

[ykulazhenkov]

The CI failure is not related (should be fixed by https://github.com/k8snetworkplumbingwg/sriov-network-operator/pull/785)