feat: upscaling using drs system

[doodlum]

Summary by CodeRabbit

• New Features

  • Built-in upscaling (DLSS, FSR, XeSS) with optional frame‑generation, new upscaling shaders, UI and settings.

• Improvements

  • VR-aware per‑eye rendering, dynamic‑resolution support, runtime‑scaled sampling counts, and per‑frame adaptive light clustering.
  • Shadow variance reporting and refined sampling for improved shadow fidelity.

• Bug Fixes

  • More reliable depth/refraction upscaling, DOF/refraction sampling, water depth handling, and shader dispatch consistency.

• Chores

  • Removed legacy submodule, added package dependencies, updated/removed license files, and added .gitignore entry.