refactor(examples): Rename and simplify legacy DSC example

- Renames `dsc_example.py` to `legacy_dsc_analysis_example.py` to
  mark it as a basic, inherited script.
- Removes the local `DSCSegmentAnalyzer` class and its redundant logic.
- Simplifies the script to perform a single analysis run on the
  entire dataset, demonstrating the direct use of the library's
  core analysis classes.
- Adds a note at the top of the file clarifying its legacy status.

Author: PPeitsch