Expand network assessment and RPS analysis guidance in sizing documentation

What does this MR do?

Improves sizing assessment documentation with clearer guidance for network capacity and RPS analysis edge cases:

• Add guidance to assess baseline traffic alongside peaks for network capacity decisions; Update recording templates to capture both baseline and peak network measurements - 795c5682
• Add fallback instructions when RPS queries timeout in high-activity environments 215ec447
• Exclude GraphQL controller from Web RPS requests - see https://gitlab.com/gitlab-com/gl-infra/software-delivery/operate/team-tasks/-/issues/1#note_2854016715
• Add complex RPS example showing cost-vs-risk decision when peak and sustained RPS are significantly different 091f22a9

Related issues

https://gitlab.com/gitlab-com/gl-infra/software-delivery/operate/team-tasks/-/issues/1#note_2850279381 and https://gitlab.com/gitlab-com/gl-infra/software-delivery/operate/team-tasks/-/work_items/2

Author's checklist

• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• If you're adding a new page, add the product availability details under the H1 topic title.
• 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.