Add diagnostic RepeatCompilation utility

To be able to stress test, benchmark and diagnose issues with specific compilations, it would be invaluable to have a diagnostic flag and compile command to repeat any or all JIT compilation an arbitrary but configurable number of times.

-XX:CompileCommand=option,java.lang.String::hashCode,intx,RepeatCompilation,10000

It doesn't matter much if the compiled code is installed on the first or last compilation, as long as the compilation itself is repeatable.

To facilitate experiments on minimal "Hello World" style apps, the repeated compilation should honor -Xbatch and not shut down until the requested number of compilations has been performed.