* use more convenient mk_substs function
	* remove type annotations
	* use map_bound one level farther outside
	* style improvements

Or at least, more properly. I think I left one or two FIXMEs still in
there.

cc #32730

In general having all these different structs for "origins" is not
great, since equating types can cause obligations and vice-versa.  I
think we should gradually collapse these things. We almost certainly
also need to invest a big more energy into the `error_reporting` code to
rationalize it: this PR does kind of the minimal effort in that
direction.

The warnings have already reached stable

The test rfc1592_deprecated is covered by `bad_sized` and
`unsized6`.

Fixes #33242
Fixes #33243

Split Ty::is_empty method into is_never and is_uninhabited

Refactor `FnCtxt::autoderef` to use an external iterator and to not
register any obligation from the main autoderef loop, but rather to
register them after (and if) the loop successfully completes.

Fixes #24819
Fixes #25801
Fixes #27631
Fixes #31258
Fixes #31964
Fixes #32320
Fixes #33515
Fixes #33755

this commit should be reverted after a release cycle

Automated conversion using the untry tool [1] and the following command:

```
$ find -name '*.rs' -type f | xargs untry
```

at the root of the Rust repo.

[1]: https://github.com/japaric/untry