[jdk21u-dev] RFR: 8343101: Rework BasicTest.testTemp test cases

[Goetz Lindenmaier]

I backport this for parity with 21.0.7-oracle

I include follow-up JDK-8343178, without that the test does not compile.

Two clean backports.

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Commit messages:
 - Backport follow up 8343178
 - Backport a95374f588149d80068275a496ba4aa04b3bb4fd

Changes: https://git.openjdk.org/jdk21u-dev/pull/1278/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1278&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343101
  Stats: 68 lines in 2 files changed: 34 ins; 17 del; 17 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1278.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1278/head:pull/1278

PR: https://git.openjdk.org/jdk21u-dev/pull/1278