RFR: 8258246: sun.net.www.ParseUtil.decode throws java.lang.IllegalArgumentException: Error decoding percent encoded characters

[Fabian Meumertzheim]

`URLClassPath` called into `ParseUtil.fileToEncodedURL`, which misencoded characters with a four byte UTF-8 representation. Replacing that function with `toPath().toUri().toURL()` (and removing it, since its only used once) results in correct encoding for all Unicode characters.

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Commit messages:
 - 8258246: sun.net.www.ParseUtil.decode
 - Add and update tests

Changes: https://git.openjdk.org/jdk/pull/23383/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23383&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8258246
  Stats: 222 lines in 4 files changed: 197 ins; 18 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/23383.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23383/head:pull/23383

PR: https://git.openjdk.org/jdk/pull/23383