RFR: 8273242: (test) Refactor to use TestNG for RuntimeTests ExecCommand tests

[Roger Riggs]

The ExecCommand test of Runtime.exec is difficult to maintain; the parallel arrays are hard to keep in sync.
This cleanup converts to use TestNG DataProviders and other improvements.

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Commit messages:
 - 8273242: Refactored ExecCommand to use TestNG DataProvider for cases

Changes: https://git.openjdk.java.net/jdk/pull/5335/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5335&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273242
  Stats: 270 lines in 1 file changed: 137 ins; 97 del; 36 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5335.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5335/head:pull/5335

PR: https://git.openjdk.java.net/jdk/pull/5335