GnuPg Extended Key Format; code analysis workflows

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (main@155b865). Click here to learn what that means. Patch has no changes to coverable lines.

:exclamation: Current head a758c46 differs from pull request most recent head c0dd8e3. Consider uploading reports for the commit c0dd8e3 to get more accurate results

Additional details and impacted files

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[maxirmx]

This PR implements:

• Codecov, coverity, CodeQL workflows and related fixes including 99% test coverage of the library (@ronaldtse Please move codecov and coverity to projects setting, thank you)
• Support for GnuPG extended key format syntax. Although it is something outside of pure SEXP scope, I believe its better to put it here for the sake of future maintainability.