Add Python GRPC interface support for creating and managing custom segment
intervals for multi-segment wells. This provides API parity with the existing
GUI functionality.
Changes:
- Add createInterval() method to RimCustomSegmentIntervalCollection
- Add GRPC method addCustomSegmentInterval to RimcWellPathCompletionSettings
- Add validation to prevent creating intervals with start_md >= end_md
- Add Python test test_custom_segment_intervals.py with validation test
- Add usage example to modeled_well_path.py
Follows the pattern established by diameter roughness intervals.
Fixes#13398.
Kristian Bendiksen