Adds jtreg tests for `Bfloat16.toString()`. The tests cover special values, representative finite values, boundary cases for standard and scientific notation, NaN payloads, and round-trip verification for all Bfloat16 bit patterns. Additionally, they verify that the results returned by the static and instance `toString` methods are consistent.
------------- Commit messages: - 8375224: Add tests for Bfloat16.toString() - 8375224: Add tests for Bfloat16.toString() - 8375224: Add tests for Bfloat16.toString() - 8375224: Add tests for Bfloat16.toString() Changes: https://git.openjdk.org/valhalla/pull/2235/files Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2235&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8375224 Stats: 139 lines in 1 file changed: 139 ins; 0 del; 0 mod Patch: https://git.openjdk.org/valhalla/pull/2235.diff Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2235/head:pull/2235 PR: https://git.openjdk.org/valhalla/pull/2235
