How to open the lightbulb via shortcut?

The correct command editor.action.quickFix. The default binding on Windows looks like this:

{ "key": "ctrl+.", "command": "editor.action.quickFix",
                   "when": "editorTextFocus" }

On Mac it's CMD + ..

If you're a JetBrains junkie and can't imagine not hammering on Alt+Enter all day long, then you can re-map the default (Ctrl+.) easily enough.

Open the File menu and select Preferences then Keyboard Shortcuts.

Type editor.action.quickFix into the search box:

Click the pen icon, or right-click and select Change Keybinding.

Enter your preferred shortcut into the dialog that appears, then press Enter.

You should end up with something that looks like: