print_tracing_info() does not use Unified Logging for output

The two options TraceYoungGenTime and TraceOldGenTime were not converted to use Unified Logging. Looking at old documentation they were planned to be changed to use the tag-set gc+summary, but it seems to have been forgotten.

Both GenCollectedHeap::print_tracing_info() and ParallelScavengeHeap::print_tracing_info() uses the flags and if enabled print information on tty.

The tag "summary" is not used anywhere else and looking at print_tracing_info for G1 it uses "gc+remset+exit" and "gc+marking" for the information printed so there is no real rule to follow. I suggest using "gc+heap+exit" for this output.