Rollup merge of #128536 - Zalathar:print-cleanup, r=Nadrieril

Preliminary cleanup of `WitnessPat` hoisting/printing

Follow-up to #128430.

The eventual goal is to remove `print::Pat` entirely, but in the course of working towards that I made so many small improvements that it seems wise to let those be reviewed/merged on their own first.

Best reviewed commit-by-commit, most of which should be pretty simple and straightforward.

r? ``@Nadrieril``

compiler/rustc_pattern_analysis/src/lib.rs

@@ -5,6 +5,7 @@
 // tidy-alphabetical-start
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
+#![cfg_attr(feature = "rustc", feature(let_chains))]
 // tidy-alphabetical-end
 
 pub mod constructor;