gh-151945: Fix reference warnings in http.cookiejar and http.server docs

[harjothkhara]

Fixes the Sphinx nit-picky reference warnings for
Doc/library/http.cookiejar.rst and Doc/library/http.server.rst, and
removes both files from Doc/tools/.nitignore so future regressions are
caught by CI.

Approach:

• Documented targets are qualified with their owning class, e.g.
  Cookie.version, CookiePolicy.rfc2965/hide_cookie2, the
  urllib.request.Request methods and attributes, and
  urllib.response.addinfourl.info.
• References with no documented target become inline literals: the removed
  get_origin_req_host method, and the undocumented http.server members
  server_name, server_port, list_directory, guess_type and
  index_pages. I'm happy to document any of these instead if a reviewer
  prefers.

Verified with a full nit-picky docs build: both files now emit zero
warnings, and Doc/tools/check-warnings.py --fail-if-regression --fail-if-improved passes.

Documentation-only reference fix, so no Misc/NEWS.d entry (skip news).

Disclosure: I used AI assistance on this change; I've reviewed it and can
explain it.

• Issue: Fix all Sphinx reference warnings in Doc/library/http.{cookiejar,server}.rst #151945

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #33398163 | 📁 Comparing 901c4f1 against main (df2538a)

  🔍 Preview build  

2 files changed

± library/http.cookiejar.html
± library/http.server.html

[StanFromIreland]

Please check for people already working on issues, @picnixz is assigned to this. I'm afraid I'm going to close.

[harjothkhara]

Sorry about that. I saw the assignment but noticed other assigned sub-issues here have open community PRs (like #151961 on #151943), so I wasn't sure it was a hard claim. Happy to defer to @picnixz.

The patch is done and verified: both files build clean in nit-picky mode and check-warnings.py --fail-if-regression --fail-if-improved passes. So if @picnixz hasn't started, it's ready to review. If they have, I'll close this. I'm also glad to take an unassigned sub-issue instead, like Doc/whatsnew/ in #151942 which has no PR yet.

[picnixz]

Inactually wanted to work on the HTTP server part so they can claim the cookiejar part.

[harjothkhara]

Thanks @picnixz — opened #152816 for the http.cookiejar half. http.server is all yours.