In order to inform future perf improvements and prevent regressions,
lets add some benchmarks that stress `impl Debug for str`.

Also sort the features.

I tried simplifying `RegionCtxt`, which led me to finding that the
fields are printed in `sccs_info`.

The comment mentions that `ReBound` and `ReVar` aren't expected here.
Experimentation with the full test suite indicates this is true, and
that `ReErased` also doesn't occur. So the commit introduces `bug!` for
those cases. (If any of them show up later on, at least we'll have a
test case.)

The commit also remove the first sentence in the comment.
`RePlaceholder` is now handled in the match arm above this comment and
nothing is printed for it, so that sentence is just wrong. Furthermore,
issue rust-lang#13998 was closed some time ago.

xz crate consist of simple reexport of xz2 crate. Why? Idk.

The type name has changed.

It's unused.

The use of `Binder` was removed in the recent rust-lang#123900, but the comment
wasn't removed at the same time.

Thus eliminating a `FIXME` comment.

This requires exporting the interpreter macros so they can be used with
`use crate::interpret::*`.

Add benchmarks for `impl Debug for str`

In order to inform future perf improvements and prevent regressions, lets add some benchmarks that stress `impl Debug for str`.

---

As I am currently working on improving the perf in rust-lang#121150, its nice to have these benchmarks.

Writing them, I also saw that escapes are written out one char at a time, even though other parts of the code are already optimizing that via `as_str`, which I intend to do as well as a followup improvement.

r? `@cuviper`
☝🏻 as you were also assigned to rust-lang#121150, CC `@the8472` if you want to steal the review :-)

…middle, r=saethlin

Remove `#[macro_use] extern crate rustc middle` from numerous crates

Because explicit importing of macros via `use` items is nicer (more standard and readable) than implicit importing via `#[macro_use]`. This PR mops up some cases I didn't get to in rust-lang#124511.

r? `@saethlin`

… r=bjorn3

`rustc_target` cleanups

Minor improvement I found while looking at this code.

r? ``@lqd``

Eliminate some `FIXME(lcnr)` comments

In some cases this involved changing code. In some cases the comment was able to removed or replaced.

r? `@lcnr`

opt-dist: use xz2 instead of xz crate

xz crate consist of simple reexport of xz2 crate. Why? Idk.

Totally not a backdoor.

analyse visitor: build proof tree in probe

see inline comments

fixes rust-lang#124791
fixes rust-lang#124702

r? ``@compiler-errors``

…errors

always use `GenericArgsRef`

r? ``@compiler-errors``