Test: Reindent all lines

[rebornix]

Test for #18958

• any os @pjmeyer
• any os @aeschli

Complexity: 3

Things to note:

• We don't set any keybindings for this command, please run it from command palette
• This command doesn't support multiple languages in one single file right now.
• Make sure the file you are working on has indentation rules set, like TypeScript or Ruby.