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.

library/core/src/panicking.rs

@@ -267,16 +267,14 @@ fn assert_failed_inner(
 
     match args {
         Some(args) => panic!(
-            r#"assertion failed: `(left {} right)`
-  left: `{:?}`,
- right: `{:?}`: {}"#,
-            op, left, right, args
+            r#"assertion `left {op} right` failed: {args}
+  left: {left:?}
+ right: {right:?}"#
         ),
         None => panic!(
-            r#"assertion failed: `(left {} right)`
-  left: `{:?}`,
- right: `{:?}`"#,
-            op, left, right,
+            r#"assertion `left {op} right` failed
+  left: {left:?}
+ right: {right:?}"#
         ),
     }
 }

tests/ui/macros/assert-eq-macro-msg.rs

@@ -1,7 +1,7 @@
 // run-fail
-// error-pattern:assertion failed: `(left == right)`
-// error-pattern: left: `2`
-// error-pattern:right: `3`: 1 + 1 definitely should be 3
+// error-pattern:assertion `left == right` failed: 1 + 1 definitely should be 3
+// error-pattern:  left: 2
+// error-pattern: right: 3
 // ignore-emscripten no processes
 
 fn main() {

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() {

tests/ui/macros/assert-matches-macro-msg.rs

@@ -1,7 +1,7 @@
 // run-fail
-// error-pattern:assertion failed: `(left matches right)`
-// error-pattern: left: `2`
-// error-pattern:right: `3`: 1 + 1 definitely should be 3
+// error-pattern:assertion `left matches right` failed: 1 + 1 definitely should be 3
+// error-pattern:  left: 2
+// error-pattern: right: 3
 // ignore-emscripten no processes
 
 #![feature(assert_matches)]

tests/ui/macros/assert-ne-macro-msg.rs

@@ -1,7 +1,7 @@
 // run-fail
-// error-pattern:assertion failed: `(left != right)`
-// error-pattern: left: `2`
-// error-pattern:right: `2`: 1 + 1 definitely should not be 2
+// error-pattern:assertion `left != right` failed: 1 + 1 definitely should not be 2
+// error-pattern:  left: 2
+// error-pattern: right: 2
 // ignore-emscripten no processes
 
 fn main() {

tests/ui/macros/assert-ne-macro-panic.rs

@@ -1,7 +1,7 @@
 // run-fail
-// error-pattern:assertion failed: `(left != right)`
-// error-pattern: left: `14`
-// error-pattern:right: `14`
+// error-pattern:assertion `left != right` failed
+// error-pattern:  left: 14
+// error-pattern: right: 14
 // ignore-emscripten no processes
 
 fn main() {

tests/ui/test-attrs/test-panic-abort-nocapture.run.stderr

@@ -1,11 +1,11 @@
 thread 'main' panicked at $DIR/test-panic-abort-nocapture.rs:33:5:
-assertion failed: `(left == right)`
-  left: `2`,
- right: `4`
+assertion `left == right` failed
+  left: 2
+ right: 4
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 thread 'main' panicked at $DIR/test-panic-abort-nocapture.rs:27:5:
-assertion failed: `(left == right)`
-  left: `2`,
- right: `4`
+assertion `left == right` failed
+  left: 2
+ right: 4
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 testing321

tests/ui/test-attrs/test-panic-abort.run.stdout

@@ -18,9 +18,9 @@ testing123
 ---- it_fails stderr ----
 testing321
 thread 'main' panicked at $DIR/test-panic-abort.rs:38:5:
-assertion failed: `(left == right)`
-  left: `2`,
- right: `5`
+assertion `left == right` failed
+  left: 2
+ right: 5
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace