RFR: 8368846: java/io/File/createTempFile/TargetDirectory fails when run by root user [v2]

[Francesco Andreuzzi]

> The test checks whether writing to a read-only directory throws a `IOException`. This test is not applicable when the user running the test is root. Thus, I propose to skip it.
> 
> I converted the class to several JUnit tests, so we can use `@DisabledIf`.

Francesco Andreuzzi has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - review
 - Merge branch 'master' into JDK-8368846
 - nn
 - cc
 - convert to junit and skip

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27542/files
  - new: https://git.openjdk.org/jdk/pull/27542/files/1a0b5065..8b828646

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27542&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27542&range=00-01

  Stats: 16358 lines in 642 files changed: 9600 ins; 3265 del; 3493 mod
  Patch: https://git.openjdk.org/jdk/pull/27542.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27542/head:pull/27542

PR: https://git.openjdk.org/jdk/pull/27542