fix: Path Resolution and Region Parsing (#3849)

This proposal introduces several key improvements to 
TexturePackerAtlas
to make it more robust when working with modular projects, flutter_gen,
and various TexturePacker export settings.

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Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>