accept direct path to interpreter as search path

[eleanorjboyd]

Currently, to search the python environments extension sends directory paths to the Python Environment Tool (PET) via the configure() RPC call. The workspaceSearchPaths setting defaults to "./**/.venv" — a glob pattern that is resolved against each workspace folder and then passed to PET as environmentDirectories. PET then crawls those directories looking for Python environments.

Proposed change: Instead of sending a .venv folder path as a search directory, send the path to the Python executable inside the environment ./**/{bin,Scripts}/python{,.exe} and have PET accept an executable path as a valid search input.