Remove all usages of java.util.UUID.randomUUID()

java.util.UUID.randomUUID() uses a "cryptographically strong pseudo random number generator", which reads from /dev/urandom (or even /dev/random in older Java versions), and then computes an expensive cryptographic digest on the bytes it read.

We don't need a cryptographically strong random number, so we can use org.infinispan.commons.util.Util.threadLocalRandomUUID() instead.