RFR: 8306711: Improve diagnosis of `IntlTest` framework [v2]

[Justin Lu]

> Please review changes to the IntlTest (test framework) class. 
> 
> These changes include
> - Logging the actual exception + stack trace. Previously, the test framework would throw `InvocationTargetException` but hide the actual underlying exception of the failing test unless the test class was ran with -nothrow.
> - Sorting the tests, ensuring for any given run, the tests are ran in the same order. (In [JDK-8305853](https://bugs.openjdk.org/browse/JDK-8305853) it was discovered that on Windows, the test framework would execute tests in a random order each time).
> - Improving output.

Justin Lu has updated the pull request incrementally with two additional commits since the last revision:

 - Revert changes that may affect extending test classes
 - Add back toHexString (used by some tests)

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13655/files
  - new: https://git.openjdk.org/jdk/pull/13655/files/9ef1cc4f..e89740cc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13655&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13655&range=00-01

  Stats: 22 lines in 1 file changed: 18 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13655.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13655/head:pull/13655

PR: https://git.openjdk.org/jdk/pull/13655