RFR: 8294839: Disable StressLongCountedLoop in compiler/loopopts/TestRemoveEmptyLoop.java

[Emanuel Peter]

As I have explained in [JDK-8294838](https://bugs.openjdk.org/browse/JDK-8294838), `-XX:StressLongCountedLoop=200000000` leads to a timeout in `compiler/loopopts/TestRemoveEmptyLoop.java` because an int-loop is transformed into a long-loop, but the loop is not collapsed/removed because we only remove empty int-loops.

This is a sub-task of [JDK-8294838](https://bugs.openjdk.org/browse/JDK-8294838), where we hope to implement empty loop removal for LongCountedLoops.

Manually tested the test with and without the flag.
Running more tests now.

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Commit messages:
 - 8294839: Disable StressLongCountedLoop in compiler/loopopts/TestRemoveEmptyLoop.java

Changes: https://git.openjdk.org/jdk/pull/10569/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10569&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294839
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10569.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10569/head:pull/10569

PR: https://git.openjdk.org/jdk/pull/10569