Implement workspace.workspaceFile extension API

[alvsan09]

This first implementation returns the Uri location of the workspace
file even if it is untitled (i.e. saved on a temporary default
location).

Fixes: #8994

Signed-off-by: Alvaro Sanchez-Leon alvaro.sanchez-leon@ericsson.com

What it does

Introduces support for the plugin API: 'vscode.workspace.workspaceFile'

How to test

An test plugin that calls this API is available from: plugin

Once installed issue the command: "Test: Echo Workspace"

1. Try the command in multi-root projects and make sure a Uri with the proper location of the workspace file is returned
2. Try the command in a project not using multi-roots and verify that no Uri is provided.
3. Open a project directory and use "Save workspace as" to convert it to a multi-root, try the command and verify it Uri is provided.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[alvsan09]

The recent commit adds a new event (onWorkspaceLocationChanged) in order to get notifications for the action "Save as" applied to a work space.

[vince-fugnitto]

I verified the changes and they work well 👍

I verified the following conditions:

Use-Case	Result
No Workspace	The API correctly returns undefined
Non Multi-Root Workspace	The API correctly returns undefined
Unsaved Multi-Root Workspace	The API correctly returns the URI of the temporary workspace file location (untitled)
Saved Multi-Root Workspace	The API correctly returns the URI of the saved workspace file location

[alvsan09]

Hi @kittaakos,
The latest commit addresses your comments, please let me know in case there are any more items to clarify.
Regards

[kittaakos]

Thank you for the patch, @alvsan09 👍