Upcoming metadata changes in V8 7.6

[cjihrig]

The V8 7.6 update requires the following adjustments to the postmortem debugging metadata constants:

• v8dbg_class_FixedTypedArrayBase__base_pointer__Object

  • Field moved from FixedTypedArrayBase to JSTypedArray.
  • Postmortem tools should use v8dbg_class_JSTypedArray__base_pointer__Object.
  • Refs: https://github.com/v8/v8/commit/70bd7cf0ef618621c16ae3f5ba2db614ac8ef996

• v8dbg_class_FixedTypedArrayBase__external_pointer__uintptr_t

  • Field moved from FixedTypedArrayBase to JSTypedArray.
  • Add new constant: v8dbg_class_JSTypedArray__external_pointer__uintptr_t
  • Refs: https://github.com/v8/v8/commit/70bd7cf0ef618621c16ae3f5ba2db614ac8ef996

• v8dbg_class_Map__instance_descriptors_offset

  • Underlying constant was renamed to kInstanceDescriptorsOffset.
  • Postmortem tools should not need to update anything for this constant.
  • Refs: https://github.com/v8/v8/commit/15a7e04eec8b98c0430960a966a57d1b2ea4aa76

Refs: https://github.com/nodejs/node/pull/28016

[No9]

No longer required but capturing these types of changes is open for discussion in https://github.com/nodejs/llnode/issues/412