RFR: 8283422: Create a new test for JDK-8254790 [v2]

[Sergey Bylokhov]

> The [JDK-8254790](https://bugs.openjdk.java.net/browse/JDK-8254790) initially was reported on macOS.
> It was found by the "javax/xml/crypto/dsig/GenerationTests.java" test which for some reason worked fine on Linux/Windows most? of the time.
> 
> I tried to run that test on Linux/Windows many times on a few systems and it always pass. Also, I got the same result for the tier1...tier4 tests.
> 
> I have found that the easiest way to reproduce the crash is to pass the result of the string.indexOf to the str.charAt when the heap is big enough. The test below[1] trigger the crash 1000 time in a row on win/lin on systems I have tested.
> 
> I am not sure what is the best way to contribute to the test, should I create a stand-alone test like[1], or update an existing test as I did for the first version of this PR?
> 
> [1]:
> 
> package compiler.intrinsics.string;
> 
> import static jdk.test.lib.Asserts.assertTrue;
> 
> public final class TestStringIndexOfLargeHeap {
>     static final int[] data = new int[Integer.MAX_VALUE / 2];
>     public static void main(String[] args) throws Exception {
>         test('a');
>         test('\ubeef');
>     }
>     private static void test(char ch) {
>         String str = ("0123456789" + ch).repeat(100);
>         for (int i = 0; i < 1_000_000; ++i) {
>             assertTrue(ch == str.charAt(str.indexOf(ch)));
>         }
>     }
> }

Sergey Bylokhov 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 four additional commits since the last revision:

 - Request 8G of heap
 - Merge branch 'master' into JDK-8283422
 - Add vm.bits == "64"
 - Initial version

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7883/files
  - new: https://git.openjdk.java.net/jdk/pull/7883/files/78c76a4e..ab2fbc35

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7883&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7883&range=00-01

  Stats: 106494 lines in 1407 files changed: 86986 ins; 16137 del; 3371 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7883.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7883/head:pull/7883

PR: https://git.openjdk.java.net/jdk/pull/7883