[vector] RFR(T/S) 8242889: test/jdk/jdk/incubator/vector/VectorConversionTests.java fails by timeout

[Ekaterina Pavlova]

Hello,

test/jdk/jdk/incubator/vector/VectorConversionTests.java is very large test
and in most cases it fails by timeout with default jtreg settings. It could
take more than 10 mins which is more than default jtreg timeout. This test
is not auto-generated from templates so I just split the test into 5 smaller
ones (each consisting of 576 test cases):

  Vector64ConversionTests.java
  Vector128ConversionTests.java
  Vector256ConversionTests.java
  Vector512ConversionTests.java
  VectorMaxConversionTests.java


Please review the changes:

       JBS: https://bugs.openjdk.java.net/browse/JDK-8242889
    webrev: http://cr.openjdk.java.net/~epavlova//8242889/webrev.00/index.html
   testing: tested by running new tests


thanks,
-katya