[roll] Roll third_party/pigweed Reland "docs: Enable Doxylink"

This is a reland of commit ed98e925da046f4ecfe802e890efb0258253f256

https://pwrev.dev/299993 was reverted because the local macOS ARM docs
build was failing. As of https://pwrev.dev/309760 that tryjob coverage
gap is now filled. The root issue was the hardcoded tagfile path in
//docs/doxygen/Doxyfile that change #299993 introduced. This hardcoded
path is invalid on macOS ARM. The new OUTDIR feature introduced in
TendTo/rules_doxygen#30 lets us configure this
path properly for all host OSes.

Original-Bug: 434937497

Original change's description:
> docs: Enable Doxylink
>
> Doxylink is a lightweight Sphinx extension that makes it easy
> to link from the main pigweed.dev site (powered by Sphinx)
> to the pigweed.dev/doxygen subsite (powered by Doxygen).
>
> Original-Bug: 426012010
>
> Change-Id: I49c6c66a8bbb45dc05a47df0e526a5d5acf5a5a3
> Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/299993
> Pigweed-Auto-Submit: Kayce Basques <[email protected]>
> Tests-Not-Needed: Kayce Basques <[email protected]>
> Copybara-Verified: Copybara Prod <[email protected]>
> Commit-Queue: Kayce Basques <[email protected]>
> Lint: Lint 🤖 <[email protected]>
> Reviewed-by: Armando Montanez <[email protected]>

Original-Bug: 426012010
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/309434
Presubmit-Verified: CQ Bot Account <[email protected]>
Original-Revision: 494717f520908dc9d351dc612b9741270d3f117d

Rolled-Repo: https://fuchsia.googlesource.com/third_party/pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 4bdcd99f0c0c75..494717f520908d
Roller-URL: https://cr-buildbucket.appspot.com/build/8707415919095582833
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I5a66790d9e3e72a28a4b89167ceb6f2708bb543a
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1338284
Commit-Queue: GI Roller <[email protected]>

Author: Kayce Basques

manifests/third_party/all

@@ -415,7 +415,7 @@
              path="third_party/pigweed/src"
              remote="https://fuchsia.googlesource.com/third_party/pigweed.googlesource.com/pigweed/pigweed"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="4bdcd99f0c0c754c4aba19928a7192a393df7c74"/>
+             revision="494717f520908dc9d351dc612b9741270d3f117d"/>
     <project name="third_party/github.com/google/python_portpicker"
              path="third_party/python_portpicker/src"
              remote="https://fuchsia.googlesource.com/third_party/github.com/google/python_portpicker"