Always capture helm uninstall output so that errors contain meaningful info

[craigwalton-dsit]

The quiet parameter of uninstall() is designed to work the same was as the Docker Compose implementation in Inspect - the idea being that the user shouldn't see helm uninstall output in most cases (except if they ran inspect sandbox cleanup k8s or the eval was cancelled/errored).

Users have previously shared logs or screenshots of RuntimeError: Helm uninstall failed. {"release": "bmkvavf7", "result": "not captured"}. Usually this is a red herring (documented here) but the "not captured" bit is unhelpful. The reason the helm uninstall output was not captured is that the uninstall()'s quiet parameter was False so the stdout/stderr of the command will have been written directly to the process's stdout/stderr.

This PR:

• Always captures stdout/stderr from helm uninstall subprocesses, and "forwards" it to stdout/stderr only if quiet=False
• Improves the documentation of the uninstall function - in particular around the behaviour of quiet.

[jasongwartz-aisi]

nice improvement!