[load testing] adjust ES heap size (#101906)

* [load testing] increase es heap to 2g

* update default simulation

* [heap size] 4g

* [heap size] 6g

* [load testing] es heap size 8g

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

Author: dmlemeshko

x-pack/test/load/config.ts

@@ -30,6 +30,7 @@ export default async function ({ readConfigFile }: FtrConfigProviderContext) {
     esTestCluster: {
       ...xpackFunctionalTestsConfig.get('esTestCluster'),
       serverArgs: [...xpackFunctionalTestsConfig.get('esTestCluster.serverArgs')],
+      esJavaOpts: '-Xms8g -Xmx8g',
     },
 
     kbnTestServer: {

x-pack/test/load/runner.ts

@@ -18,7 +18,7 @@ const simulationPackage = 'org.kibanaLoadTest.simulation';
 const simulationFIleExtension = '.scala';
 const gatlingProjectRootPath: string =
   process.env.GATLING_PROJECT_PATH || resolve(REPO_ROOT, '../kibana-load-testing');
-const simulationEntry: string = process.env.GATLING_SIMULATIONS || 'DemoJourney';
+const simulationEntry: string = process.env.GATLING_SIMULATIONS || 'branch.DemoJourney';
 
 if (!Fs.existsSync(gatlingProjectRootPath)) {
   throw createFlagError(