RFR: 8336756: Improve ClassFile Annotation writing

[Chen Liang]

Clean up annotation writing in classfile api: remove the redundant `Util.Writable` interfaces.

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Commit messages:
 - 8336756: Improve ClassFile Annotation writing

Changes: https://git.openjdk.org/jdk/pull/20635/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20635&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336756
  Stats: 123 lines in 3 files changed: 24 ins; 76 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/20635.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20635/head:pull/20635

PR: https://git.openjdk.org/jdk/pull/20635