Rollup merge of #137423 - Urgau:imprv-pretty-hir, r=compiler-errors

Improve a bit HIR pretty printer

This PR improve (a bit) the HIR pretty printer.

It does so by:
 - Not printing elided lifetimes (those are not expressible in surface Rust anyway)
 - And by rendering implicit self with the shorthand syntax

I also tried fixing some indentation and other things but gave up for now.

Best reviewed commit by commit.

Author: jhpratt