[jhanca-robotecai]

What does this PR do?

Port RobotecSplineTools to O3DE 2605; verify Smoothing and LevelModificationTools working. Only the first one required updates due to changes in ROS2 Gem. Additionally, I removed bundled csv.hpp header and added FetchContent and fixed the topics in both subscriber and publisher.

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How was this PR tested?

• LevelModificationTools: switching between prefab variants at runtime, including clearing with an out-of-range variant.
• Smoothing: the No Smoothing, Average and Damping methods.
• SplineTools: CSV import and export in the Editor; the publisher and subscriber in game mode, with namespaced topics.

I suggest the reviewer checks only SplineTools, which has real changes.

Screenshots / Logs / Supporting Evidence (if applicable)

Add screenshots, terminal logs, or relevant links to builds/tests as needed.

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Committer Checklist

Please confirm the following before marking this PR as ready for review:

• Code changes are well-documented
• Tests have been added or updated
• Code owners file and CI config were updated if new Gem was added
• The code is formatted according to the project's style guide
• The version number has been updated according to the contributing guidelines