RFR: 8304837: Classfile API throws IOOBE for MethodParameters attribute without parameter names [v2]

[Hannes Greule]

> After merging master into https://github.com/openjdk/jdk/pull/9862, we encountered test failures (e.g., https://github.com/SirYwell/jdk/actions/runs/4500940829/jobs/7923018438#step:9:2541). The Classfile API tries to read from constant pool index 0 if a MethodParameters attribute has an entry without name.
> 
> The fix is simply using `readUtf8EntryOrNull` instead of `readUtf8Entry`. The related code already correctly handles nullability.
> 
> I didn't find an appropriate test class so I added a new one. Let me know if there's a better place or if the test can be improved somehow.
> 
> As I don't have a JBS account, someone needs to create a bug report there for me. Thanks.

Hannes Greule has updated the pull request incrementally with one additional commit since the last revision:

  Apply suggestions from code review
  
  Co-authored-by: liach <7806504+liach at users.noreply.github.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13167/files
  - new: https://git.openjdk.org/jdk/pull/13167/files/4a94bb17..f4b8062c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13167&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13167&range=00-01

  Stats: 2 lines in 2 files changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13167.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13167/head:pull/13167

PR: https://git.openjdk.org/jdk/pull/13167