RFR: JDK-8289798: Update to use jtreg 7 [v4]

[Christian Stein]

> Please review the change to update to using jtreg 7.
> 
> The primary change is to the `jib-profiles.js` file, which specifies the version of jtreg to use, for those systems that rely on this file. In addition, the `requiredVersion` has been updated in the various `TEST.ROOT` files.

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Update configure to check for jtreg 7 or later

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9393/files
  - new: https://git.openjdk.org/jdk/pull/9393/files/468f0bd3..1f6f4a7d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9393&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9393&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9393.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9393/head:pull/9393

PR: https://git.openjdk.org/jdk/pull/9393