docs: maintenance on user search docs

[hazel-nut]

Description

consolidates user search docs into three articles:

• search for specific users by id/email
• list and search for users with query strings
• query string syntax reference and examples

removes information duplicated from management api reference (e.g. on pagination).

Testing

best reviewed by looking over the three pages in the preview rather than looking at the diff in this PR.

already approved by the PM for search.

Checklist

• I've read and followed CONTRIBUTING.md.
• I've tested the site build for this change locally.
• I've made appropriate docs updates for any code or config changes.
• I've coordinated with the Product Docs and/or Docs Management team about non-trivial changes.

[github-actions]

Summary

Status	Count
🔍 Total	24
✅ Successful	6
⏳ Timeouts	0
🔀 Redirected	0
👻 Excluded	18
❓ Unknown	0
🚫 Errors	0
⛔ Unsupported	0
Full Github Actions output

[nick-gagliardi]

is there a need to keep this page?

[hazel-nut]

it has the auto-generated overview of child pages, so i think it serves as a nice landing page