Use new environment variables API

[karrtikr]

Instead of using the temporary hack to get environment variables, use microsoft/vscode-python#20056.

cc/ @heejaechang

[rchiodo]

Is this related to the client move?

[karrtikr]

Yes

[debonte]

@heejaechang, I see this issue was moved to "Done". Can it be closed?

[heejaechang]

there is one more place we can use it (server using the API through custom LSP to resolve env variables) or we resolve things like $workspaceroot in the middleware. but that work is separate work I guess.

[heejaechang]

this specific issue is done. this one is about pythonPath

[karrtikr]

this specific issue is done. this one is about pythonPath

I opened this for environment variable API, pythonPath is separate.

But I guess we can close this in favor of https://github.com/microsoft/pyrx/issues/3376.