[jdk21u-dev] RFR: 8324672: Update jdk/java/time/tck/java/time/TCKInstant.java now() to be more robust

[Goetz Lindenmaier]

I backport this for parity with 21.0.7-oracle

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Commit messages:
 - Backport e94e3bba3932f3d92c0a135d333d1ccd6e72b964

Changes: https://git.openjdk.org/jdk21u-dev/pull/1206/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1206&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324672
  Stats: 16 lines in 1 file changed: 11 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1206.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1206/head:pull/1206

PR: https://git.openjdk.org/jdk21u-dev/pull/1206