RFR: 8370216: Fix of new File("").exists() causes undefined behavior in libraries

[Brian Burkhalter]

Add a system property, `jdk.io.File.failIfEmptyPath`, which when `true` reverts to legacy, pre-JDK 25 behavior, as to how `java.io.File` handles an empty pathname string.

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Commit messages:
 - 8370216: Fix of new File().exists() causes undefined behavior in libraries

Changes: https://git.openjdk.org/jdk/pull/28158/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28158&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370216
  Stats: 151 lines in 4 files changed: 101 ins; 0 del; 50 mod
  Patch: https://git.openjdk.org/jdk/pull/28158.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28158/head:pull/28158

PR: https://git.openjdk.org/jdk/pull/28158