boards/linum-stm32h753bi: Add zbus board integration and configuration

[JorgeGzm]

Summary

Integration of the zbus message bus port (apache/nuttx-apps#3743) on
top of the iterable sections infrastructure (#19927), in two commits:

1. zbus linker support: include/nuttx/linker/zbus.ld + a
   tools/Config.mk hook (CONFIG_ZBUS_LINKER_INSERT), an optional
   zero-touch mode using GNU ld INSERT AFTER for boards that do not
   include the common fragments (constraints documented in the file);
   plus the zbus Sphinx documentation.
2. linum-stm32h753bi adoption (first adopter board): 2 #include
   lines in flash.ld and a zbus board configuration enabling the
   zbus example and its cmocka test suite, reproducible with
   ./tools/configure.sh linum-stm32h753bi:zbus.

Impact

• Users: zbus becomes usable out of the box on the
  linum-stm32h753bi through the new :zbus configuration; any other
  board can adopt it the same way (two linker-script lines, or the
  INSERT mode with no board edit).
• Existing boards/configs: none. The included fragments expand to
  nothing unless CONFIG_ZBUS is enabled (verified: the stock :nsh
  map has zero zbus sections), and the Config.mk hook is inert unless
  CONFIG_ZBUS_LINKER_INSERT=y.
• Build process: Make and CMake both supported (both preprocess the
  board linker script, so the #include lines work on either).
• Hardware: only the linum-stm32h753bi board is touched.
• Documentation: zbus application pages and a zbus entry in the
  board configuration list.
• Tooling: the reused zbus SVG diagrams are added to the
  .codespellrc skip list (their embedded base64 raster data trips the
  spell checker with false positives).
• Security / compatibility: no changes to existing runtime code.

Testing

Target: linum-stm32h753bi (STM32H753BI),

• :zbus build (Make and CMake): OK, the three _zbus_*_list sections
  collected name-sorted in flash as required by the zbus VDED algorithm.
• On hardware: the 16-test zbus cmocka suite passes twice
  in the same boot and the zbus example produces the expected output,
  with the fourth message correctly masked for the listener and the
  listener notified before the subscriber:

nsh> zbus
zbus: publishing 5 messages to acc_chan
zbus:  listener: x=1 y=10 z=100
zbus:  subscriber: x=1 y=10 z=100
zbus:  listener: x=2 y=20 z=200
zbus:  subscriber: x=2 y=20 z=200
zbus:  listener: x=3 y=30 z=300
zbus: listener masked
zbus:  subscriber: x=3 y=30 z=300
zbus: listener unmasked
zbus:  subscriber: x=4 y=40 z=400
zbus:  listener: x=5 y=50 z=500
zbus:  subscriber: x=5 y=50 z=500
zbus: done

• INSERT mode validated in a standalone ld harness (placement, sorting,
  no overlap).
• tools/checkpatch.sh -c -u -m -g on both commits (nxstyle +
  codespell, same flags as CI): all checks pass. sphinx-build -W:
  clean.

Depends-On: apache/nuttx-apps#3743
Depends-On: #19927

[github-actions]

MemBrowse Memory Report

No memory changes detected for:

• arduino-mega2560
• esp32-devkitc
• hifive1-revb
• mirtoo
• qemu-armv8a
• qemu-intel64
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb

[xiaoxiang781216]

@JorgeGzm could you split iterator section from zbus to new pr?

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• system/zbus: Port the Zephyr zbus message bus to NuttX nuttx-apps#3743 @ 69a6237b74

CI run: https://github.com/apache/nuttx/actions/runs/32439921078

[linguini1]

Do not list "new files". This is visible in the diff already. Please review the AI-generated PR descriptions and revise them for correctness and simplicity.

[JorgeGzm]

@JorgeGzm could you split iterator section from zbus to new pr?

Done, the PR #19927 whas created.

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• system/zbus: Port the Zephyr zbus message bus to NuttX nuttx-apps#3743 @ 69a6237b74

CI run: https://github.com/apache/nuttx/actions/runs/32515058484

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• system/zbus: Port the Zephyr zbus message bus to NuttX nuttx-apps#3743 @ 69a6237b74
• include/nuttx: Add link-time iterable sections infrastructure #19927 @ 7b31777

CI run: https://github.com/apache/nuttx/actions/runs/32531266071

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• system/zbus: Port the Zephyr zbus message bus to NuttX nuttx-apps#3743 @ 5d9cd00bad
• include/nuttx: Add link-time iterable sections infrastructure #19927 @ 7b31777

CI run: https://github.com/apache/nuttx/actions/runs/32757958806

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• system/zbus: Port the Zephyr zbus message bus to NuttX nuttx-apps#3743 @ dfd91d6e53
• include/nuttx: Add link-time iterable sections infrastructure #19927 @ 7f9181b

CI run: https://github.com/apache/nuttx/actions/runs/32880838739