Implement the JFR ObjectAllocationSample event - step1

[LinHu2016]

Base on JFR event specification (from SAP JFR Events
17):

• Introduce a new GC hook J9HOOK_MM_OBJECT_ALLOCATION_SAMPLING_INTERNAL
  that is functionally identical to J9HOOK_MM_OBJECT_ALLOCATION_SAMPLING
  but is designated internal-only (JVM use only, no Java code runs in
  callbacks). This prevents the hook's registration from disabling JIT OSR
  safe-point optimization in vmhook.c.

• Define the event structure J9JFRObjectAllocationSample in
  j9nonbuilder.h and J9JFR_EVENT_TYPE_OBJECT_ALLOCATION_SAMPLE id in
  j9consts.h

• Register a JFR-internal callback jfrObjectAllocationSample() on
  J9HOOK_MM_OBJECT_ALLOCATION_SAMPLING_INTERNAL in
  startJFRRecording(), implement the callback to write a
  J9JFRObjectAllocationSample event with
  a stack trace into the per-thread buffer, and unregister it in
  stopJFRRecording().

• new jfrObjectSamplingBytesGranularity in GCExtensionBase
  new _jfrTraceAllocationBytes in EnvironmentBase for tracking and
  triggering J9JFRObjectAllocationSample event.

• JFR specifies ObjectAllocationSample throttling in events-per-second
  (default: 150/s, profiling: 300/s). The GC layer works in bytes. A
  conversion is needed: from the JVM's current heap allocation rate
  (bytes/sec), derive a byte-granularity interval such that approximately
  N events/second are emitted. JVM startup uses a reasonable default
  byte interval 512KB. new objectAllocationSampleThrottleRate (throttle
  value (events/s)) in vm->jfrState.

• New function j9gc_set_jfr_allocation_sampling_interval() to let JFR
  enable/disable/reconfigure the threshold.

• Add a periodic recalibration step in jfrSamplingThreadProc()'s
  1-second tick block, Read total bytes allocated since last GC, Compute
  new byte interval: newInterval = allocatedBytes / (throttleRate *
  elapsedSinceLastGC).

• handle the case JVMTI sampling is also active, arm the TLH top at the
  nearer of the two next-trigger points so that neither sampler fires
  late.

#depends on: eclipse-omr/omr#8407
#fix: #24213
Signed-off-by: lhu linhu@ca.ibm.com