Permit Installing .NET via a package.json file

[nagilson]

Intro

Extensions that rely on .NET often have a slow startup time due to our existing API, which needs to be invoked in typescript code.
This is per a request from the Copilot for Azure extension.

Change

For extensions that want the .NET runtime to be installed as soon as possible, they can now also make an API request in their package.json. #1935

They should add a IDotnetAcquireContext object in a section titled 'x-dotnet-acquire' to do so. They don't need to include the requestingExtensionId, since this is already in their package.json,

This should go at the root of a package.json, and not in the contributes section.

"x-dotnet-acquire": {
    "version": "8.0",
    "mode": "aspnetcore"
}

We run the install on startup and also whenever a new extension is installed via the onDidChange API. https://code.visualstudio.com/api/references/vscode-api#Extension<T>

Testing

You can easily test this by modifying the SDK extension and adding this, then packging it with vsce, installing it, and running the Runtime Extension under the Debug tab. If you do so, you will see that:

If you install a new extension, the request is made. From my testing, it also doesn't grab focus away from the terminal which is great, I figured that would be a huge pain point. Something to still watch out for as it needs to be improved: #1935

(Before installing extension)

(On install)

If you had already installed the extension, the request is also made.
(On Opening VS Code)

Tests

It's a bit hard to test this functionality comprehensively, so while there's a very basic test, I've added a page about it in our vendor testing as well.

[jacdavis]

[nagilson]

Thanks for your review. We still need to get the branding for the versions PR approved and a few other minor PRs for the release, so I expect it will take a few days.