RFR: 8304181: Constant Descriptors for MethodHandles::classData and classDataAt

[liach]

Add Constant Descriptors for DirectMethodHandleDesc of MethodHandles::classData and classDataAt in ConstantDescs. This facilitates easier access of class data via condy in Classfile API-generated bytecode. Most other constant bootstrap methods provided in the JDK, notably from `ConstantBootstraps`, already have constant descriptors in ConstantDescs.

Context: https://mail.openjdk.org/pipermail/classfile-api-dev/2023-March/000235.html

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Commit messages:
 - ConstantDescs for MethodHandles.classData and classDataAt

Changes: https://git.openjdk.org/jdk/pull/13033/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13033&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304181
  Stats: 16 lines in 1 file changed: 16 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13033.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/13033/head:pull/13033

PR: https://git.openjdk.org/jdk/pull/13033