18.9 - Stop uploading packages to PackageCloud

What does this MR do and why?

Describe in detail what merge request is being backported and why

Backport the following MRs to 18.9 to stop uploading packages to PackageCloud:

• Stop uploading Omnibus packages to PackageCloud... (!9225 - merged)
• ci: Do not allow pulp jobs to fail (!9232 - merged)
• Remove Pulp jobs dependency on PC (!9247 - merged)
• Manual release fips packages to Pulp (!9253 - merged)

Ref:

• https://gitlab.com/gitlab-org/omnibus-gitlab/-/work_items/9552+
• https://gitlab.com/gitlab-org/build/team-tasks/-/work_items/177+

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The original MR has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).