RFR: 8347167: Implementation in com.sun.net.httpserver.Headers.normalize() can be improved

[Josiah Noel]

Following the direction outlined in the net-dev discussion, I've updated the `com.sun.net.httpserver.Headers.normalize()` method to no longer allocate a superfluous char array when the header is already normalized.

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Commit messages:
 - formatting
 - Optimize header normalization

Changes: https://git.openjdk.org/jdk/pull/27276/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27276&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347167
  Stats: 30 lines in 2 files changed: 22 ins; 1 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27276.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27276/head:pull/27276

PR: https://git.openjdk.org/jdk/pull/27276