MINOR Increase JUnit max forks and memory for CI (#18560)

Increase the max number of forks for each JUnit task to 4. Also increase
the amount of memory given to forked workers to 3g.

Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

.github/actions/run-gradle/action.yml

@@ -88,7 +88,7 @@ runs:
         ./.github/scripts/thread-dump.sh &
         timeout ${TIMEOUT_MINUTES}m ./gradlew --build-cache --continue --no-scan \
         -PtestLoggingEvents=started,passed,skipped,failed \
-        -PmaxParallelForks=2 \
+        -PmaxParallelForks=4 \
         -PmaxTestRetries=$TEST_RETRIES -PmaxTestRetryFailures=10 \
         -Pkafka.test.catalog.file=$TEST_CATALOG \
         -Pkafka.test.run.new=$RUN_NEW_TESTS \

build.gradle

@@ -525,7 +525,7 @@ subprojects {
     maxParallelForks = maxTestForks
     ignoreFailures = userIgnoreFailures
 
-    maxHeapSize = defaultMaxHeapSize
+    maxHeapSize = "3g"
     jvmArgs = defaultJvmArgs
 
     // KAFKA-17433 Used by deflake.yml github action to repeat individual tests