feat: add --collect-coverage-from option to include untested files in coverage

[meylis1998]

Summary

Implements feature request #418 to add a --collect-coverage-from option that allows users to choose whether coverage is collected from imported files only or all files in the project.

Changes

• Added CoverageCollectionMode enum with imports (default) and all modes
• Added --collect-coverage-from option to both Flutter and Dart test commands
• Implemented file discovery and LCOV enhancement to include untested files with 0% coverage
• Respects existing --exclude-coverage and --report-on options
• Updated tests to verify functionality

Usage Examples

# Default behavior (unchanged - imports only)
very_good test --coverage

# Include all files in coverage
very_good test --coverage --collect-coverage-from all

# Enforce 100% coverage across all files
very_good test --min-coverage 100 --collect-coverage-from all

# Exclude generated files from coverage
very_good test --coverage --collect-coverage-from all --exclude-coverage '**/*.g.dart'

Key Features

• ✅ Backward compatible (defaults to imports mode)
• ✅ Works with both Flutter and Dart projects
• ✅ Includes all .dart files in 'all' mode, showing 0% for untested files
• ✅ Compatible with existing coverage options
• ✅ Respects glob patterns from --exclude-coverage

Files Modified

• lib/src/cli/test_cli_runner.dart - Core implementation
• lib/src/commands/test/test.dart - Flutter test command
• lib/src/commands/dart/commands/dart_test_command.dart - Dart test command
• lib/src/cli/flutter_cli.dart - Flutter CLI integration
• lib/src/cli/dart_cli.dart - Dart CLI integration
• test/src/commands/test/test_test.dart - Flutter test updates
• test/src/commands/dart/commands/dart_test_test.dart - Dart test updates

Closes #418

[meylis1998]

Hey @marcossevilla! 👋

When you get a chance, would you mind taking a look at this PR? I'd really appreciate your feedback.

Thanks!