Add code linting using Laravel Pint

[AndrewKostka]

Bug: T394986

[outdooracorn]

Looking through the changes this linting applies, I'm happy with most of them. I would vote to change a few things:

1. headsDownCamelCase instead of snake_case for function names - this should remove a lot of changes
2. keep function's opening brace ({) on the same line as the function definition
3. keep a space around the string concatenation operator (.) - I think it makes it look less like a full stop and more like an operator.