Add local Gradle daemon and parallelism tuning

Enables parallel projects, a bounded worker pool, and a larger daemon
heap so concurrent compilation and test forks (see the conformance
test worker-isolation fix) have enough headroom.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TtiGhPTwQoK8CQkf7yffVm

Author: flemming-n-larsen

gradle.properties

@@ -0,0 +1,11 @@
+# Allow independent projects and tasks to run concurrently.
+org.gradle.parallel=true
+
+# Keep enough workers available for concurrent compilation and test forks.
+org.gradle.workers.max=20
+
+# Reuse the Gradle daemon between invocations.
+org.gradle.daemon=true
+
+# Give concurrent work enough heap while retaining a bounded worker pool.
+org.gradle.jvmargs=-Xmx2g -XX:MaxMetaspaceSize=512m -XX:+HeapDumpOnOutOfMemoryError