Detect non-returning functions

[tmr232]

This greatly affects the flowgraph, and should be handled.
However, it is something we definitely don't wanna do in our code, as it'll be different per-language.

I think the best way to go about it is to see if we can use the IDE to query this - detect calls and the actual functions that are being called.
Then, if all we need to add is "known non-returning functions", it's not that bad.
But type inference and similar tasks should not be part of this project for now.

[tmr232]

Seems the relevant VSCode API is the built-in command vscode.executeDeclarationProvider:

// Get the active text editor
const editor = vscode.window.activeTextEditor;
if (!editor) {
  vscode.window.showInformationMessage('No editor is active');
  return;
}

// Get the current position of the cursor
const position = editor.selection.active;

// Get the definition at the current position
const definitions = await vscode.commands.executeCommand<vscode.Location[]>(
  'vscode.executeDefinitionProvider',
  editor.document.uri,
  position
);