RFR: 8367284: (fs) Support current working directory target in SecureDirectoryStream.move [v3]

[Brian Burkhalter]

> Change `java.nio.file.SecureDirectoryStream.move` so that, instead of throwing a `NullPointerException` if the `targetdir` parameter is `null`, it considers a non-absolute path passed via `targetpath` as being relative to the current working directory.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8367284: Address comments about test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27178/files
  - new: https://git.openjdk.org/jdk/pull/27178/files/7c21d87e..8b9a5df2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27178&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27178&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27178.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27178/head:pull/27178

PR: https://git.openjdk.org/jdk/pull/27178