SpringBoot Use virtual threads in Docker Compose support if enabled

There's thread creation in org.springframework.boot.docker.compose.core.ProcessRunner using the ReaderThread.

Comment From: mhalbritter

Those could be virtual threads, as they don't contain synchronized and only call JDK APIs to read from a stream. They are only used when we need to shell out to read stdout and stderr. I don't think we gain much here when switching them to virtual threads.