[8u] RFR 8177628: Opensource unit/regression tests for ImageIO

[Zhengyu Gu]

Hi,

I would like to backport these tests to 8u. Although, it does not show 
up as Oracle parity, but a few Oracle parities depend on it.

The original JDK9 patch applies cleanly, but I modified some of tests, 
removed @modules annotations.

Original bug: https://bugs.openjdk.java.net/browse/JDK-8177628
Original patch: http://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/e748c6a2d2e6

8u webrev: http://cr.openjdk.java.net/~zgu/JDK-8177628-8u/webrev.00/

Test:
   Ran new tests on Linux x86_64, all passed


Thanks,

-Zhengyu