RFR: 8309838: Classfile API Util.toBinaryName and other cleanup

[Chen Liang]

Thanks to @exe-boss for the reviews in #13082. This cleanup patch fixed the typos you pointed out and removed other redundancies in classfile Util as well.

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Commit messages:
 - 8309838: Classfile API Util.toBinaryName and other cleanup

Changes: https://git.openjdk.org/jdk/pull/14412/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14412&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309838
  Stats: 77 lines in 4 files changed: 1 ins; 62 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/14412.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14412/head:pull/14412

PR: https://git.openjdk.org/jdk/pull/14412