RFR: 8319463: ClassSignature should have superclass and superinterfaces as ClassTypeSig [v2]

[Chen Liang]

> Discovered while writing a test for #16513 that `ClassSignature.superclassSignature()` does not return a `ClassTypeSig`, yet [JVM Spec](https://docs.oracle.com/javase/specs/jvms/se21/html/jvms-4.html#jvms-4.7.9.1-4100) requires it to be one. This patch adds such a requirement to the accessors, factories, and the parsing logic.

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into feature/class-signature-elements
 - 8319463: ClassSignature should have superclass and superinterfaces as ClassTypeSig

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16514/files
  - new: https://git.openjdk.org/jdk/pull/16514/files/77464793..3db563c6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16514&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16514&range=00-01

  Stats: 718541 lines in 3208 files changed: 139028 ins; 508573 del; 70940 mod
  Patch: https://git.openjdk.org/jdk/pull/16514.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16514/head:pull/16514

PR: https://git.openjdk.org/jdk/pull/16514