Increase maxium heap size for testsuite (#692)

The `-Xmx` flag sets the maximum heap-size of the jvm. The change in this commit increase this limit for the unittest-runner from 2 gigabyte to 4 gigabyte, after reports of the testsuite failing with out-of-memory on certain systems.

Co-authored-by: lc <[email protected]>

Author: lacgit

pom.xml

@@ -254,7 +254,7 @@
                 <version>${chartfx.surefire.version}</version>
                 <configuration>
                     <!-- Jacoco prepare-agent builds some command-line params without which jacoco will not instrument. Hence it is important to add those command-line params here (${argLine} holds those params) -->
-                    <argLine>${argLine} -Duser.language=en -Duser.country=US -Xms256m -Xmx2048m -XX:G1HeapRegionSize=32m -Djava.awt.headless=true -Dtestfx.robot=glass -Dtestfx.headless=true -Dprism.order=sw</argLine>
+                    <argLine>${argLine} -Duser.language=en -Duser.country=US -Xms256m -Xmx4096m -XX:G1HeapRegionSize=32m -Djava.awt.headless=true -Dtestfx.robot=glass -Dtestfx.headless=true -Dprism.order=sw</argLine>
                     <forkCount>1</forkCount>
                     <rerunFailingTestsCount>3</rerunFailingTestsCount>
                     <runOrder>random</runOrder>