fix(thermal_camera): Fixed Gaussian noise for thermal camera. (backport #597)

[mergify]

🦟 Bug fix

Summary

Thermal camera with Gaussian noise segfaults like this:

(2026-03-17 14:28:15.239) [error] [Noise.cc:63] Image noise requested. Please use ImageNoiseFactory::NoiseModel instead
Stack trace (most recent call last) in thread 685223:
#9    Object "[0xffffffffffffffff]", at 0xffffffffffffffff, in 
#8    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x76f339322c6b, in 
#7    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x76f339295aa3, in 
#6    Object "/lib/x86_64-linux-gnu/libstdc++.so.6", at 0x76f33423ddb3, in 
#5    Object "/opt/ros/kilted/opt/gz_sim_vendor/lib/gz-sim-9/plugins/libgz-sim-sensors-system.so", at 0x76f311be23ce, in 
#4    Object "/opt/ros/kilted/opt/gz_sim_vendor/lib/libgz-sim9-rendering.so.9", at 0x76f311b451eb, in gz::sim::v9::RenderUtil::Update()
#3    Object "/opt/ros/kilted/opt/gz_sim_vendor/lib/gz-sim-9/plugins/libgz-sim-sensors-system.so", at 0x76f311beabed, in 
#2    Object "/opt/ros/kilted/opt/gz_sim_vendor/lib/gz-sim-9/plugins/libgz-sim-sensors-system.so", at 0x76f311bed4c0, in 
#1    Object "/opt/ros/kilted/opt/gz_sensors_vendor/lib/libgz-sensors9-thermal_camera.so.9", at 0x76f311a83607, in gz::sensors::v9::ThermalCameraSensor::SetScene(std::shared_ptr<gz::rendering::v9::Scene>)
#0    Object "/opt/ros/kilted/opt/gz_sensors_vendor/lib/libgz-sensors9-thermal_camera.so.9", at 0x76f311a7d146, in 
Segmentation fault (Address not mapped to object [(nil)])

This PR fixes it by correctly using ImageNoiseFactory instead of NoiseFactory. This was probably forgotten in 6a00a58 .

This PR also adds the skipping of noise in case it is zero, as was done in #450 for other camera types.

Checklist

• Signed all commits for DCO
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• Added tests
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This is an automatic backport of pull request #597 done by Mergify.