RFR: 8265356: need code example for getting canonical constructor of a Record

[Tagir F.Valeev]

I decided to show a complete static method in the example, so it could be copied to user utility class as is. Not sure if it's reasonable to add `assert cls.isRecord();` there. Also I don't know whether there's a limitation on max characters in the sample code. Probable a line break in `static <T extends Record>\nConstructor<T> getCanonicalConstructor(Class<T> cls)` is unnecessary.

---
Aside from this PR, I've found a couple of things to clean up in `java.lang.Class`:
1. There's erroneous JavaDoc link in `getSimpleName()` JavaDoc (introduced by @jddarcy in #3038). It should be `#isArray()` instead of `isArray()`.
2. Methods Atomic::casAnnotationType and Atomic::casAnnotationData have unused type parameters `<T>`.
3. Probably too much but AnnotationData can be nicely converted to a record! Not sure, probably nobody wants to have `java.lang.Record` initialized too early or increasing the footprint of such a basic class in the metaspace, so I don't insist on this.


    private record AnnotationData(
        Map<Class<? extends Annotation>, Annotation> annotations,
        Map<Class<? extends Annotation>, Annotation> declaredAnnotations,
        // Value of classRedefinedCount when we created this AnnotationData instance
        int redefinedCount) {
    }


Please tell me if it's ok to fix 1 and 2 along with this PR.

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Commit messages:
 - 8265356: need code example for getting canonical constructor of a Record

Changes: https://git.openjdk.java.net/jdk/pull/3556/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3556&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265356
  Stats: 13 lines in 1 file changed: 13 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3556.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3556/head:pull/3556

PR: https://git.openjdk.java.net/jdk/pull/3556