Improve DefaultModelProcessor error reporting for alternative parsers

[gnodet]

When multiple model parsers are registered (e.g., for YAML or TOML POMs) and all parsers fail to parse a POM file, the error message now provides detailed information about each parser's failure.

Changes

• Changed modelParsers from List<ModelParser> to Map<String, ModelParser> to preserve parser names for better error messages
• Added buildDetailedErrorMessage() method that generates a comprehensive error report including:
  • The POM file path
  • The number of parsers attempted
  • Each parser's error with line/column information when available
  • The default XML reader's error
• Updated all call sites to use Map.of() instead of List.of()
• Added unit tests for the new error reporting functionality

Example Error Output

When a YAML POM file fails to parse:

Unable to parse POM /path/to/pom.yaml
        Tried 2 parsers:
          yaml) YAML parsing failed at line 5, column 10: Invalid YAML syntax
          toml) TOML parsing failed at line 3, column 7
          default) XML reader also failed: XML parsing failed

This improves debugging when using alternative POM formats by showing exactly why each parser failed, rather than just the final XML error.

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Pull Request opened by Augment Code with guidance from the PR author

[gnodet]

💚 All backports created successfully

Status	Branch	Result
✅	master

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