tweak new test suite output
- Make the entire "## Running ui tests ..." green, including the target.
- Fix double-space in `testname.rs .. ok`.
- Make the final summary a bit more like compiletest-rs, in particular the newlines around it
- Use the term "ignored" consistently, rather than "skipped"
r? `@oli-obk`
Add a command line flag to avoid printing to stdout and stderr
This is practical for tests that don't actually care about the output and thus don't want it intermingled with miri's warnings, errors or ICEs
fixes#2083
Replace unneeded use of `ref` in favor of "match ergonomics"
The signature of `check_shim` is very amenable to this.
```rust
fn check_shim<'a, const N: usize>(…) -> InterpResult<'tcx, &'a [OpTy<'tcx, Tag>; N]>
```
Instead of:
```rust
let &[ref ptr, ref flags] = this.check_shim(…)?;
```
we can write it just as:
```rust
let [ptr, flags] = this.check_shim(…)?;
```
add -Zmiri-strict-provenance
This implements [strict provenance](https://github.com/rust-lang/rust/issues/95228) in Miri. The only change is that casting an integer to a pointer does not even attempt to produce a good provenance for the given address; instead, it always uses the invalid provenance. This stricter than even `-Zmiri-tag-raw-pointers` in that it also rejects the following example (which does not even involve Stacked Borrows):
```rust
fn main() {
let x = 22;
let ptr = &x as *const _ as *const u8;
let roundtrip = ptr as usize as *const u8;
let _ = unsafe { roundtrip.offset(1) };
}
```
The new flag also implies `-Zmiri-tag-raw-pointers` since the only reason one would *not* want to tag raw pointers is to support ptr-int-ptr roundtrips.
Note that the flag does *not* check against ptr-to-int *transmutes*; that still requires `-Zmiri-check-number-validity`. You can also check for strict provenance *without* Stacked Borrows by adding `-Zmiri-disable-stacked-borrows`.
The new "Miri hard mode" flags for maximal checking are `-Zmiri-strict-provenance -Zmiri-check-number-validity`. (Add `-Zmiri-symbolic-alignment-check` if you feel extra spicy today.)
