Defaults sets all options back to their defaults.
This can be useful when using CopyToTempDir or Convert but not wanting to inherit any options from the previous PulumiTest.
WithCache enables caching of the stack state to the given path.
If the path already exists, the cached stack state will be used instead of executing the run.
If the path does not exist, the stack state will be written to the cache path after executing the run.