RFR: 8366584: Add an InstanceKlass::super() method that returns InstanceKlass*

[Ioi Lam]

By adding an `InstanceKlass* InstanceKlass::super()` method to shadow `Klass* Klass:super()`, this PR makes it possible to simplify the following code


InstanceKlass* ik;
InstanceKlass* s;
s = InstanceKlass::cast(ik->super()); // before JDK-8366024 
s = ik->java_super(); // after JDK-8366024 


to


s = k->super();


So you no longer need to do casting or need to understand what `java_super()` is.

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Commit messages:
 - 8366584: Add an InstanceKlass::super() method that returns InstanceKlass*

Changes: https://git.openjdk.org/jdk/pull/27037/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27037&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366584
  Stats: 91 lines in 28 files changed: 8 ins; 2 del; 81 mod
  Patch: https://git.openjdk.org/jdk/pull/27037.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27037/head:pull/27037

PR: https://git.openjdk.org/jdk/pull/27037