Rollup merge of #116859 - Nilstrieb:more-more-funny-pretty-printers, r=oli-obk

Make `ty::print::Printer` take `&mut self` instead of `self`

based on #116815

This simplifies the code by removing all the `self` assignments and
makes the flow of data clearer - always into the printer.
Especially in v0 mangling, which already used  `&mut self` in some
places, it gets a lot more uniform.

Author: matthiaskrgr