RFR: 8353923: (fs) Further improve performance of URI -> Path conversion (win)

[Brian Burkhalter]

If the path portion of a `URI` permits, then simply replace all `'\'` with `'/'` instead of completely parsing the path.

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Commit messages:
 - 8353923: (fs) Further improve performance of URI -> Path conversion (win)

Changes: https://git.openjdk.org/jdk/pull/24638/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24638&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353923
  Stats: 37 lines in 1 file changed: 35 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/24638.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24638/head:pull/24638

PR: https://git.openjdk.org/jdk/pull/24638