ci: Weekly lockfile generation CI job

[sl0thentr0py]

Issues

• part of: Acknowledge dependency pinning audit for sentry-ruby #2961
• part of: RUBY-180

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[linear-code]

RUBY-180

[dingsdax]

lgtm

I wonder though if this could by DRY-ed; steps are always the same (checkout, setup, bundlce, lock, upload) only gem name, matrix and lockfile name change, extracting the gen-* steps into a reusable workflow?

or separate workflow files per gem?

[sl0thentr0py]

will do later