[clang] [LifetimeSafety] Improve destroyed and invalidated diagnostic notes (PR #204900)

[Utkarsh Saxena via cfe-commits]

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@@ -95,7 +95,8 @@ void conditional_operator_lifetimebound(int cond) {
     int a, b;
     p = identity(cond ? &a    // expected-warning {{local variable 'a' does not live long enough}}
                       : &b);  // expected-warning {{local variable 'b' does not live long enough}}
-  }                           // expected-note 2 {{destroyed here}}
+  }                           // expected-note {{local variable 'a' is destroyed here}}
+                              // expected-note at -1 {{local variable 'b' is destroyed here}}
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usx95 wrote:

nit: I am not a big fan of `expected-note at -1`, it disturbs the indent of the text specially if there are other similar warning on the same line.

Consider using trailing `\`:
```
  }                           // expected-note {{local variable 'a' is destroyed here}} \
                              // expected-note {{local variable 'b' is destroyed here}}
```

https://github.com/llvm/llvm-project/pull/204900