RFR: 8353453: URLDecoder should use HexFormat

[Patrick Strawderman]

Use `HexFormat.fromHexDigits` in URLDecoder, instead of `Integer.parseInt`.

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Commit messages:
 - Use HexFormat in URLDecoder

Changes: https://git.openjdk.org/jdk/pull/24314/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24314&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353453
  Stats: 6 lines in 1 file changed: 1 ins; 4 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24314.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24314/head:pull/24314

PR: https://git.openjdk.org/jdk/pull/24314