Rollup merge of #107102 - compiler-errors:new-solver-new-candidats-4, r=lcnr

Implement some more predicates in the new solver

Implement a few more goals. The subtype goal specifically is important, since it's required for this code to compile:

```
fn main() {
  let mut x = vec![];
  x.push(1i32);
}
```

(I think we emit a subtype goal here because of coercion).

Drive-by: Also implements `--compare-mode=next-solver` -- I've been using this locally a lot to find out what works and what doesn't. I'm also happy to split this out into another PR.

r? `@lcnr`

0 files changed, 0 insertions, 0 deletions