RFR: 8273242: (test) Refactor to use TestNG for RuntimeTests ExecCommand tests [v2]

[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.

Roger Riggs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Simplify file deletion
   Add enum to document test modes.
 - Merge branch 'master' into 8273242-execcommand-refactor
 - 8273242: Refactored ExecCommand to use TestNG DataProvider for cases

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5335/files
  - new: https://git.openjdk.java.net/jdk/pull/5335/files/d374449b..8dbd021e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5335&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5335&range=00-01

  Stats: 35582 lines in 1179 files changed: 24923 ins; 5611 del; 5048 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