Expose a unified way to retrieve Python Env Associated with Jupyter Notebooks

[DonJayamanne]

Currently there's a private API that Pylance gets to use in order to determine the Python Env associated with Jupyter notebooks.
Unfortunately there are a few problems with this API:

• Its built specifically for Pylance, other extensions cannot get this same information
• Upon selecting a new Kernel, the Pylance extension won't always know that a new Python Env has been selected for a Jupyter Notebook
• The API is inconsistent, currently there's an API in Python extension to get the Python Env associated with a Uri, but Jupyter Notebooks is not part of this (when Jupyter Notebooks are also just Uris).

Pros:

• Unified approach to getting Python Environments for notebooks, Python files, workspaces etc.
• No code change for extensions consuming the Python API
• Resolves some bugs as well

Solution:

• Keep the Python extension + Jupyter Extension API internal (as today)
• Update the Python extension as follows:

export type ActiveEnvironmentPathChangeEvent = EnvironmentPath & {
    /**
     * Workspace folder the environment changed for.
     * Or Resource the environment changed for.
     */
    readonly resource: WorkspaceFolder | Uri | undefined;
};

Internally, the call to getActiveEnvironmentPath(resource?: Resource): EnvironmentPath; would now handle Uris a little differently. If the Uri is a notebook Uri, then get the interpreter from Jupyter extension (using existing code).
The check if the Uri is a notebook can optionally be passed into Jupyter as well, i.e. keep it super simple.