4601: Introduce `toggle inlay hints` vscode command r=matklad a=Veetaha

Users now can assign a shortcut for this command
via the general vscode
keybindings ui or `keybindings.json` file

<details>
<summary>Demo</summary>

![demo](https://user-images.githubusercontent.com/36276403/82768941-b4fd1c80-9e3a-11ea-9d5b-a40fa1e4dbc6.gif)

</details>

<details>
<summary>Howto assign a shortcut</summary>

![demo2](https://user-images.githubusercontent.com/36276403/82769350-c8a98280-9e3c-11ea-8a95-1266a539826d.gif)


</details>

Closes: #4599

Co-authored-by: veetaha <veetaha2@gmail.com>