Multi-Language Support: Fix read file extensions from SonarqubeAnalysis.xml

[martin-strecker-sonarsource]

Follow up to #2088

The implementation has the following issues:

• It uses a regex where EndsWith would be sufficient
• It matches files that shouldn't be matched:
  • File with a file extension that ends with a known extension, like e.g. invalid.ajs matches extension .js
  • File without an ending that starts with a ., e.g. file SomeDirectory\.js is matched by the .js extension
• It lacks tests for multi-extension extensions like .tar.gz

See also the discussion here #2088 (comment)