Add ability to auto update Insiders build of extension

[DonJayamanne]

Others have done this microsoft/vscode#15756 (comment)

Updating label to code health + enhancement.
I.e. even if not exposed to end users, it would be good for in-house use. Much like out of band LS installs.

[d3r3kk]

We already have the python file to do this...

[DonJayamanne]

Note: This is not for extension authors. That python file builds the extension.
This is for users of the developer build of the extension, i.e. dog fooding.
VSC doesn't provide a pre-release channel of extensions, and that's why we host our extension on a blob store, and users need to install it manually.

The benefit, is:

• We'll have a regular set of users who are constantly testing/using the dev version of the extension.
• We have the potential to get feedback before the release.

Either way, this would be great for in house developers.

UX (similar to out of band installs of LS):

• Download and install extension daily, weekly
• Manual download and install of the extension (via some command)

[DonJayamanne]

@luabud /cc

[DonJayamanne]

Will need to consider impact of downloading LS every time we update the extension (e.g. if we update extension every day, then LS will be downloaded every day).

See #4323

[DonJayamanne]

• Have a look at how C++ extension does the auto updating.

[DonJayamanne]

Prescribed Solution

• Download vsix
• Install the extension using a the command vscode.commands.executeCommand('workbench.extensions.installExtension', Uri.file('path-to-vsix'));
  • This command is available in the latest version of VS Code.

Check spec for UX