update(dummy_c): create a custom CI workflow for `dummy_c`

[Andreagit97]

What type of PR is this?

/kind cleanup

/kind design

Any specific area of the project related to this PR?

/area plugins

What this PR does / why we need it:

This change is because we cannot use codeQL autobulid mode for complex cpp plugins (see https://github.com/falcosecurity/plugins/pull/378). So the idea is to create a custom workflow for each cpp plugin (in this case dummy_c) with a build job (that runs codeQL) and a formatting job. In the same way, the k8smeta plugin will have a dedicated workflow with a build-and-test job (that runs codeQL) and a formatting job.

Which issue(s) this PR fixes:

Special notes for your reviewer:

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[github-actions[bot]]

Rules files suggestions

[poiana]

LGTM label has been added.

Git tree hash: 477cfbecbf070d252dffd185877478e75d8084b9

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Andreagit97, leogr

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