Similar to an update recently done for langtools tests, update the libraries regression tests to take advantage of the @enablePreview jtreg feature.
------------- Commit messages: - JDK-8297215: Update libs tests to use @enablePreview Changes: https://git.openjdk.org/jdk/pull/11222/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11222&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8297215 Stats: 122 lines in 36 files changed: 33 ins; 1 del; 88 mod Patch: https://git.openjdk.org/jdk/pull/11222.diff Fetch: git fetch https://git.openjdk.org/jdk pull/11222/head:pull/11222 PR: https://git.openjdk.org/jdk/pull/11222
