## Summary
This PR renames the `tab-size` configuration option to `indent-width` to
express that the formatter uses the option to determine the indentation
width AND as tab width.
I first preferred naming the option `tab-width` but then decided to go
with `indent-width` because:
* It aligns with the `indent-style` option
* It would allow us to write a lint rule that asserts that each
indentation uses `indent-width` spaces.
Closes#7643
## Test Plan
Added integration test
84979f9673