perf-tool: list of all waiters in the monitorEvents

[gireeshpunathil]

It would be good to capture all the waiters info on the monitorEvents output, if need be. I suggest this to be implemented under a flag, or else can:

• clutter the output
• add performance overhead

The info_ptr field in the call to

GetObjectMonitorUsage(jvmtiEnv* env,
            jobject object,
            jvmtiMonitorUsage* info_ptr)

is a structure like this:

typedef struct {
    jthread owner;
    jint entry_count;
    jint waiter_count;
    jthread* waiters;
    jint notify_waiter_count;
    jthread* notify_waiters;
} jvmtiMonitorUsage;

and the fields waiter_count and waiters have the needed info, IIUC.
/cc @mpirvu - am I right?