RFR: 8323425: JFR: Auto-generated filename doesn't work with time-limited recording

[Erik Gahlin]

Could I have a review of a PR that fixes a bug when filename is set to a directory and the recording has a duration.

Testing: jdk/jdk/jfr

Thanks
Erik

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Commit messages:
 - Updated
 - Initial

Changes: https://git.openjdk.org/jdk/pull/17360/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17360&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323425
  Stats: 150 lines in 4 files changed: 105 ins; 28 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/17360.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17360/head:pull/17360

PR: https://git.openjdk.org/jdk/pull/17360