Fix shutdown callback leak in wait_for_message

[ahcorde]

Description

rclcpp::wait_for_message registers an on-shutdown callback on the context to wake up the wait set, but never removes it. Every call leaves one more callback registered until the context shuts down.

• Remove the callback with RCPPUTILS_SCOPE_EXIT, the same way the subscription is already removed from the wait set.
• Add a regression test that checks the number of shutdown callbacks doesn't grow across calls

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Claude Opus 5.5

[github-actions]

ABI Compliance Check

✅ Verdict: compatible

Library	Verdict	Summary
libcomponent_manager.so	✅ compatible	No ABI changes detected.
librclcpp.so	✅ compatible	No ABI changes detected.
librclcpp_action.so	✅ compatible	No ABI changes detected.
librclcpp_lifecycle.so	✅ compatible	No ABI changes detected.

✅ libcomponent_manager.so — full abidiff report

Compared:

• Base: lib-base/libcomponent_manager.so
• Head: lib-pr/libcomponent_manager.so @ 0f6b6fb

(empty report — no differences printed by abidiff)

✅ librclcpp.so — full abidiff report

Compared:

• Base: lib-base/librclcpp.so
• Head: lib-pr/librclcpp.so @ 0f6b6fb

Functions changes summary: 0 Removed (41 filtered out), 0 Changed (79 filtered out), 0 Added (19 filtered out) functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable

✅ librclcpp_action.so — full abidiff report

Compared:

• Base: lib-base/librclcpp_action.so
• Head: lib-pr/librclcpp_action.so @ 0f6b6fb

(empty report — no differences printed by abidiff)

✅ librclcpp_lifecycle.so — full abidiff report

Compared:

• Base: lib-base/librclcpp_lifecycle.so
• Head: lib-pr/librclcpp_lifecycle.so @ 0f6b6fb

(empty report — no differences printed by abidiff)

_{Updated for commit 0f6b6fb · check run · suppressions: /home/runner/work/_temp/ros2-abi-suppressions.txt}