Draft: Add SSOT for packges

What does this MR do?

1. Removes seemingly now irrelevant information about ARM64 not being fully supported yet. Seeking clarification here: &4397 (comment 1236410010)
2. Surfaces information about what packages exist for officially supported OSes
3. This information is not only not present, but this existing text on the page appears to create confusion by being easily misunderstood to mean that ALL supported ARCHes also have packages "GitLab provides arm64/aarch64 packages for some supported operating systems. You can see if your operating system architecture is supported in the table above." => These seem to be linked when they may not be as the second sentence is speaking only to being tested on an OS+arch combination.

As evidence of need - here is one partner question that I could not resolve with certainty using the supported OSes page information: &2370 (comment 1164576149)

Related issues

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• If you're adding or changing the main heading of the page (H1), ensure that the product tier badge is added.
• If you are a GitLab team member, request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are a GitLab team member and only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Reviewer's checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

If you aren't sure which tech writer to ask, use roulette or ask in the #docs Slack channel.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • Ensure a release milestone is set.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the reviews above. Maintainer's review can occur before or after a technical writer review.