Disentangle `Debug` and `Display` for `Ty`.
The `Debug` impl for `Ty` just calls the `Display` impl for `Ty`. This is surprising and annoying. In particular, it means `Debug` doesn't show as much information as `Debug` for `TyKind` does. And `Debug` is used in some user-facing error messages, which seems bad.
This commit changes the `Debug` impl for `Ty` to call the `Debug` impl for `TyKind`. It also does a number of follow-up changes to preserve existing output, many of which involve inserting
`with_no_trimmed_paths!` calls. It also adds `Display` impls for `UserType` and `Canonical`.
Some tests have changes to expected output:
- Those that use the `rustc_abi(debug)` attribute.
- Those that use the `rustc_layout(debug)` attribute.
- Those that use the `EMIT_MIR` annotation.
In each case the output is slightly uglier than before. This isn't ideal, but it's pretty weird (particularly for the attributes) that the output is using `Debug` in the first place. They're fairly obscure attributes (I hadn't heard of them) so I'm not worried by this.
For `async-is-unwindsafe.stderr`, there is one line that now lacks a full path. This is a consistency improvement, because all the other mentions of `Context` in this test lack a path.
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