This introduces breaking changes for external readers are loaded:
1. In PklProject, relative paths are resolved relative to the enclosing
PklProject file (make behavior consistent with how other settings work)
2. Make CLI flags blow away any settings set on a PklProject
3. Introduce a new `workingDir` property, which defaults to the
PklProject dir
The overall goal is to make this behavior consistent with how other
settings work.
For example, relative paths for other evaluator settings are already
relative to the project directory.
Additionally, in every other case, CLI flags will overwrite any setting
set within PklProject.
With JSpecify now a dependency of pkl-config-java, this moves the
non-null annotation to jspecify's.
This makes it simpler for users to do nullness checks, as tooling
already understands JSpecify nullness annotations.
This doesn't really make sense as part of the `Config` API.
We can maybe make class `ConfigUtils` public, but, I don't know how useful it
is anyways; it's more of an implementation detail.
Daniel Chao