Allow IntegTestClusters to run with FIPS 140 JVMs (elastic#39917)

The changes in elastic#39732 mean that nodes in the IntegTest clusters will
now run with whichever java version is defined as `runtime.java` and
not JAVA_HOME anymore.
This means that these nodes will also run in JVM with fips approved
mode enabled and as such, need to have access to the password for the
BCFKS keystore that is used as the default keystore/truststore.

This change sets the two necessary system properties.

Resolves elastic#39855

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterFormationTasks.groovy

@@ -317,6 +317,12 @@ class ClusterFormationTasks {
         // its run after plugins have been installed, as the extra config files may belong to plugins
         setup = configureExtraConfigFilesTask(taskName(prefix, node, 'extraConfig'), project, setup, node)
 
+        // If the node runs in a FIPS 140-2 JVM, the BCFKS default keystore will be password protected
+        if (project.inFipsJvm){
+            node.config.systemProperties.put('javax.net.ssl.trustStorePassword', 'password')
+            node.config.systemProperties.put('javax.net.ssl.keyStorePassword', 'password')
+        }
+
         // extra setup commands
         for (Map.Entry<String, Object[]> command : node.config.setupCommands.entrySet()) {
             // the first argument is the actual script name, relative to home