Add generation of new style header.

[Timotej Ecimovic (tecimovic)]

This is a pull request addressing: Add generation of new style header.

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Note

Generates new sl_iostream_swo_itm_8.h, updates C enum output (adding primary and legacy enums, metadata tweaks), ignores the new file, and bumps version to 1.13.2.

• Code generation (silabs-pti/build.gradle):
  • Add generation of sl_iostream_swo_itm_8.h using SL_ENUM_GENERIC with EM-prefixed values for compatibility.
  • Update debug-message-type-gen.h generation:
    • Emit primary enum with SL_DEBUG_MESSAGE_TYPE_ prefixes plus a separate legacy EM-prefixed enum.
    • Refresh header metadata (year 2025, repo URL).
  • Add clearer write logs for generated files.
• Housekeeping:
  • Ignore the new generated header in .gitignore.
  • Bump version to 1.13.2.

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