GitLab Shell: Support configuration of public key algorithms

What does this MR do?

GitLab Shell: Support public key algorithms

Allow to configure GitLab shells public_key_algorithms.

• GitLab Shell MR: gitlab-org/gitlab-shell!986 (merged)
• Omnibus equivalent: gitlab-org/omnibus-gitlab!7660 (merged)

Changelog: added

Related issues

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• Documentation created/updated.
• Tests added/updated, and test plan for scenarios not covered by automated tests.
• Equivalent MR/issue for omnibus-gitlab opened.

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• MR has a green pipeline on https://gitlab.com/gitlab-org/charts/gitlab.
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