RFR: 8342466: Improve API documentation for java.lang.classfile.attribute

[Chen Liang]

Improve documentation for `class` file attributes. This include better specification for user attributes, some more general information about attributes, such as the usage of non-JVMS attributes, and updated some attribute information in the base package too, such as Annotation and Signature.

APIDiff, Javadoc, and CSR incoming.

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Commit messages:
 - 8342466: Improve API documentation for java.lang.classfile.attribute

Changes: https://git.openjdk.org/jdk/pull/23026/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23026&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342466
  Stats: 2571 lines in 68 files changed: 1608 ins; 125 del; 838 mod
  Patch: https://git.openjdk.org/jdk/pull/23026.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23026/head:pull/23026

PR: https://git.openjdk.org/jdk/pull/23026