RFR: 8284889: runtime/cds/appcds/loaderConstraints/DynamicLoaderConstraintsTest.java#custom-cl-zgc timed out

[Calvin Cheung]

Please review this simple fix for increasing the timeout from the default 120s to 180s for the `custom-cl-zgc` test case of the DynamicLoaderConstraintsTest.java test.

Tested 200 times on linux-aarch64-debug with the following vm options:
`-XX:MaxRAMPercentage=6.25 -Xcomp -XX:+CreateCoredumpOnCrash -ea -esa -XX:CompileThreshold=100 -XX:+UnlockExperimentalVMOptions -server -XX:+TieredCompilation`

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

Commit messages:
 - 8284889: runtime/cds/appcds/loaderConstraints/DynamicLoaderConstraintsTest.java#custom-cl-zgc timed out

Changes: https://git.openjdk.java.net/jdk/pull/8367/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8367&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284889
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8367.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8367/head:pull/8367

PR: https://git.openjdk.java.net/jdk/pull/8367