RFR: 8294626: Improve URL protocol lower casing

Fri Sep 30 10:46:57 UTC 2022

Move a simple utility method from `URL` to the shared `sun.net.util.URLUtil` class, rename it for clarity and enhance it so that it returns a string literal. This helps reduce dependencies from bootstrap code on `Locale` while improving the performance and allocation pressure in certain applications.

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Commit messages:
 - Use URLUtil.lowerCaseProtocol in URLConnection
 - 8294626: Improve URL protocol lower casing

Changes: https://git.openjdk.org/jdk/pull/10506/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10506&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294626
  Stats: 42 lines in 3 files changed: 21 ins; 14 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/10506.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10506/head:pull/10506

PR: https://git.openjdk.org/jdk/pull/10506