Add report-converter --example flag and EXAMPLE_CMD interface (#4992)

[mmido6039]

Summary

Fixes #4992 by adding a standardized way for report-converter analyzers to expose example commands for generating compatible input.

What changed

• Added the EXAMPLE_CMD interface field to AnalyzerResultBase.

• Added EXAMPLE_CMD to the Ruff analyzer parser.

• Added a new --example <ANALYZER> CLI option to report-converter.

• --example works independently of the other required CLI arguments, similarly to --help and --version.

• Added documentation for Ruff and the new --example functionality.

• Added a documentation note recommending --example as the up-to-date source for analyzer example commands.

• Added CLI/interface tests covering:

  • An analyzer with an EXAMPLE_CMD.
  • An analyzer without an EXAMPLE_CMD.
  • Invalid analyzer names.
  • Enforcement that newly added analyzer parsers define EXAMPLE_CMD.

Validation

Manually verified:

• report-converter --example ruff prints the expected example command and exits successfully.
• report-converter --example pylint handles an analyzer without an example gracefully without crashing.
• Invalid analyzer names are rejected cleanly by argparse.

All 5 newly added tests pass.

The broader report-converter test suite also contains pre-existing/environment-related failures unrelated to this change, including fixture corruption and package metadata mismatches. These were verified against the unmodified codebase.

Motivation

This provides a consistent interface for analyzer-specific example commands and prevents new analyzer parsers from being added without documenting how their compatible input can be generated.