RFR: JDK-8232092 (fs) Files::isWritable returns false on a writeable root directory (win) [v3]

[Nhat Nguyen]

> I'm following up on the reviewing thread here: https://mail.openjdk.java.net/pipermail/nio-dev/2020-August/007456.html
> 
> All the tests that create symlinks are now properly checked against using `TestUtil.supportsLinks`

Nhat Nguyen has updated the pull request incrementally with two additional commits since the last revision:

 - Drop testRealPath (JDK-8213216)
 - Revert TestUtil changes and use Files.createTempDirectory directly

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/287/files
  - new: https://git.openjdk.java.net/jdk/pull/287/files/c6b539ad..ef2e1d51

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=287&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=287&range=01-02

  Stats: 46 lines in 2 files changed: 0 ins; 34 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/287.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/287/head:pull/287

PR: https://git.openjdk.java.net/jdk/pull/287