[pyoutline] Add OpenJD backend for job template serialization

Add a new PyOutline backend that serializes Outline jobs into OpenJD
2023-09 job templates. This enables running OpenCue jobs via the openjd
CLI or submitting them to OpenJD-compatible schedulers like AWS Deadline
Cloud.

- Serialize layers to OpenJD steps with CHUNK[INT] frame parameters
- Map OpenCue command tokens (#IFRAME#, #FRAMESPEC#, etc.) to OpenJD
  expressions using the EXPR extension
- Map host requirements: cores, memory, GPUs, tags, service, limits
- Map dependencies including Post layer implicit depends
- Wrap commands in bash scripts that export CUE_* environment variables
- Support Shell, ShellScript, and PyEval layer types
- Validate generated templates using openjd-model
- Launch jobs locally via openjd CLI
- Install with: pip install opencue-pyoutline[openjd]

Author: mwiebe