Added Hydrostatic Pressure sensor

[ahcorde]

🎉 New feature

Summary

I noticed that there is not Hydrostatic Pressure sensor which publish a fluidPressure message. We have Altimeter or Air Pressure.

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the feature
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• Updated Bazel files (if adding new files). Created an issue otherwise.
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Generated-by: Claude Sonnet 4.6

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[caguero]

Should we move the pure non-gazebo functionality to gz-sensors?

[azeey]

Should we move the pure non-gazebo functionality to gz-sensors?

This is not an opinion, but I'd encourage us to think about this question in the context of our recent conversations (Gazebo-classic postmortem) about the purpose of gz-sensors and the future goal of integrating it into gz-sim.