Cleaner assert_eq! & assert_ne! panic messages

Modify panic message for `assert_eq!`, `assert_ne!`, the currently unstable `assert_matches!`, as well as the corresponding `debug_assert_*` macros.

```rust
assert_eq!(1 + 1, 3);
assert_eq!(1 + 1, 3, "my custom message value={}!", 42);
```

```plain
thread 'main' panicked at $DIR/main.rs:6:5:
assertion failed: `(left == right)`
  left: `2`,
 right: `3`
```
```plain
thread 'main' panicked at $DIR/main.rs:6:5:
assertion failed: `(left == right)`
  left: `2`,
 right: `3`: my custom message value=42!
```

```plain
thread 'main' panicked at $DIR/main.rs:6:5:
assertion `left == right` failed
  left: 2
 right: 3
```

```plain
thread 'main' panicked at $DIR/main.rs:6:5:
assertion `left == right` failed: my custom message value=42!
  left: 2
 right: 3
```

This PR is a simpler subset of the #111030, but it does NOT stringify the original left and right source code assert expressions, thus should be faster to compile.

1 files changed, 3 insertions, 3 deletions

diff --git a/tests/ui/macros/assert-eq-macro-panic.rs b/tests/ui/macros/assert-eq-macro-panic.rs
index 5e505c30b35..6745290cbfc 100644
--- a/tests/ui/macros/assert-eq-macro-panic.rs
+++ b/tests/ui/macros/assert-eq-macro-panic.rs
@@ -1,7 +1,7 @@
 // run-fail
-// error-pattern:assertion failed: `(left == right)`
-// error-pattern: left: `14`
-// error-pattern:right: `15`
+// error-pattern:assertion `left == right` failed
+// error-pattern:  left: 14
+// error-pattern: right: 15
 // ignore-emscripten no processes
 
 fn main() {