Rollup merge of #82770 - m-ou-se:assert-match, r=joshtriplett

Add assert_matches macro.

This adds `assert_matches!(expression, pattern)`.

Unlike the other asserts, this one ~~consumes the expression~~ may consume the expression, to be able to match the pattern. (It could add a `&` implicitly, but that's noticable in the pattern, and will make a consuming guard impossible.)

See https://github.com/rust-lang/rust/issues/62633#issuecomment-790737853

This re-uses the same `left: .. right: ..` output as the `assert_eq` and `assert_ne` macros, but with the pattern as the right part:

assert_eq:
```
assertion failed: `(left == right)`
  left: `Some("asdf")`,
 right: `None`
```
assert_matches:
```
assertion failed: `(left matches right)`
  left: `Ok("asdf")`,
 right: `Err(_)`
```

cc ```@cuviper```

0 files changed, 0 insertions, 0 deletions