RFR: 8368331: ClassFile Signature parsing fails for type parameter with no supertype [v4]

[Chen Liang]

> Some type parameter declaration signatures in class and method generic signatures, such as `<T:R:>`, are valid per JVMS but are not accepted by either the ClassFile or the legacy core reflection parser. (Javac doesn't generate these because it always generates an Object upper bound) They can be constructed by the ClassFile API models. So it makes sense to support their parsing as supported by JVMS and our API model.

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:

 - Fix bad test merge
 - Merge branch 'master' of https://github.com/openjdk/jdk into fix/cf-typevar-parse
 - Merge branch 'master' of https://github.com/openjdk/jdk into fix/cf-typevar-parse
 - 8368331: ClassFile Signature parsing fails for type parameter with no supertype
 - More fixes
 - Fix bad docs and add more to clarify class type sig
 - Merge branch 'master' of https://github.com/openjdk/jdk into fix/cf-classtypesig-factory-classdesc
 - Fix links
 - More bugs
 - 8368050: Validation missing in ClassFile signature factories

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Changes: https://git.openjdk.org/jdk/pull/27439/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27439&range=03
  Stats: 31 lines in 2 files changed: 28 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/27439.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27439/head:pull/27439

PR: https://git.openjdk.org/jdk/pull/27439