fix(system_error_monitor): hold emergency when timeout happens

[h-ohta]

Description

When timeout happens, emergency becomes true, but emergency_holding does not become true.
I'll fix it.

Related links

TIERIV_INTERNAL_LINK: https://tier4.atlassian.net/browse/T4PB-25040

Tests performed

• change use_emergency_hold to true in system.launch.xml
  https://github.com/autowarefoundation/autoware.universe/blob/main/launch/tier4_system_launch/launch/system.launch.xml#L65
• launch psim
• echo /system/emergency/hazard_status
• kill default_ad_api to occur timeout
  ps -aux | grep default_ad_api | awk '{print $2}' | xargs kill
• confirm status transition of emergency_holding to true after 5 seconds

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[codecov]

Codecov Report

Base: 11.47% // Head: 11.45% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (756e411) compared to base (3522a10).
Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2634      +/-   ##
==========================================
- Coverage   11.47%   11.45%   -0.02%     
==========================================
  Files        1272     1272              
  Lines       88535    88668     +133     
  Branches    23320    23320              
==========================================
  Hits        10161    10161              
- Misses      67604    67737     +133     
  Partials    10770    10770              

Flag	Coverage Δ		*Carryforward flag
differential	0.00% <0.00%> (?)
total	11.47% <0.00%> (ø)		Carriedforward from 3522a10

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
...or_path_planner/src/behavior_path_planner_node.cpp	0.17% <0.00%> (ø)
...path_planner/src/scene_module/lane_change/util.cpp	0.00% <0.00%> (ø)
...em_error_monitor/src/system_error_monitor_core.cpp	0.00% <0.00%> (ø)

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[ito-san]

LGTM