RFR: 7842: policy file is missing entry for test on Windows [v2]

[Ralf Schmelter]

> This change adds an entry to the test policy file to allow acces to the temporary directory. This is needed since the surefire plugin places it files there on Windows, in contrast to other platforms where they are placed in the target/surefire directory.

Ralf Schmelter has updated the pull request incrementally with one additional commit since the last revision:

  Prepare permissions for new failsafe version und handle 8.3 names for the temp dir

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Changes:
  - all: https://git.openjdk.org/jmc/pull/410/files
  - new: https://git.openjdk.org/jmc/pull/410/files/0285f423..408d812f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmc&pr=410&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmc&pr=410&range=00-01

  Stats: 2 lines in 2 files changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jmc/pull/410.diff
  Fetch: git fetch https://git.openjdk.org/jmc pull/410/head:pull/410

PR: https://git.openjdk.org/jmc/pull/410