[Chore] Allow beforeTest hook that blocks until IPC (e.g., file sync) signals test continuation

[delsner]

Currently, the pre-test hook will be executed as a background process and the JVM process continues running without interruption. There might be cases where we want to also sync the pre-test hook with the JVM process, to wait until the pre-test hook has been completely executed (e.g., if attaching with instrumentation tool to JVM process).

The simplest way to achieve synchronization between the JVM process and the pre-test hook process would be through file synchronization, where the JVM process waits for a file to be available (by polling) and the pre-test hook process creates the file upon successful initialization.