RFR: 8297301: Cleanup unused methods in JavaUtilJarAccess [v5]

[pandaapo]

> The cache named `signerToCodeSource` in `JarVerifier` is never used now.

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

  Modify as reviews.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11072/files
  - new: https://git.openjdk.org/jdk/pull/11072/files/c4cfb499..a8fb419c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11072&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11072&range=03-04

  Stats: 249 lines in 2 files changed: 0 ins; 249 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11072.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11072/head:pull/11072

PR: https://git.openjdk.org/jdk/pull/11072