doc: minus (U+2212) instead of dash (U+002D) for negative infinity

The documentation for [`f32::NEG_INFINITY`](https://doc.rust-lang.org/std/f32/constant.NEG_INFINITY.html) contains “-∞” with a dash instead of a minus sign, “−∞” with a proper minus sign looks better with the used Source Serif Pro font. Similarly for [`f64::NEG_INFINITY`](https://doc.rust-lang.org/std/f64/constant.NEG_INFINITY.html).

Move the region_scope_tree query to librustc_passes.

Split out of rust-lang#67688.

r? @Zoxc

…-Simulacrum

Add self to .mailmap

r? @Mark-Simulacrum

Cheers.

Add error code explanation for E0477

Part of rust-lang#61137

Support `-Z ui-testing=yes/no`

`ui-testing` is now a boolean option (`-Z ui-testing=yes/no`) and can be specified multiple times with later values overriding earlier values (`-Z ui-testing=yes -Z ui-testing=no` == `-Z ui-testing=no`), so it can be set in a hierarchical way, e.g. UI testing infra may enable it by default with specific tests being able to opt-out.

This way we can remove the special opt-out support from `compiletest`.

Inspired by rust-lang#67709.