Provide a way to indicate whether a Python environment is specific to a workspace folder

[DonJayamanne]

E.g. when a local .venv is discovered and found when searching custom paths, then we must keep track of this.

Suggestions:

• Rename searchPaths to projectDirs or the like
• When we find envs in the given project dirs, then add the project dir to the env information
• Applicable for caches as well, in the future we'll know to exclude these
  Q: Who should exclude envs, client or Pet?

[DonJayamanne]

Done