Refactor in preparation for moving JAX/XLA CI to build.py
Refactor in preparation for moving JAX/XLA CI to build.py

* Move some `DockerImage` fields to arguments to `pull_and_run`
* Don't supply a default workdir
* Don't give a default for `target_patterns` in BUILD
* Rename `_DEFAULT_TARGET_PATTERNS` to `_XLA_DEFAULT_TARGET_PATTERNS`
* Move comment about cudnn9 container to a more appropriate location
