@nx/s3-cache: Provide expanded environment variable bindings

[ctvajhofman]

Summary
Provide a way to supply properties outside of the nx.json file that may need to change per environment or use case, much like what was done in #30594. Look for the environment variable after loading what's defined in the nx.json file in order to perform overrides.

Details
While being able to provide the S3 cache's configuration directly in the nx.json file is nice, when working with CI providers, an additional feature to override properties inside of the pipeline run that may or may not be initially provided or known would be beneficial.

The use case I was working on was attempting to proactively prevent cross-build pollution between PR/MR and when code is merged to the main/master branch, until I found that some settings could only be set once in the json file.