test: update postmortem metadata test for V8 7.3

The V8 7.3 update requires the following adjustments to the
postmortem debugging metadata constants:

- v8dbg_prop_idx_first was removed in
  v8/v8@1ad0cd5

- v8dbg_jsarray_buffer_was_neutered_mask was renamed to
  v8dbg_jsarray_buffer_was_detached_mask in
  v8/v8@f68ee6e

- v8dbg_jsarray_buffer_was_neutered_shift was renamed to
  v8dbg_jsarray_buffer_was_detached_shift in
  v8/v8@f68ee6e

- v8dbg_class_Map__instance_descriptors__DescriptorArray moved to
  v8dbg_class_Map__raw_instance_descriptors__DescriptorArray and
  began using ACCESSORS2 in
  v8/v8@799dfad

The following postmortem debugging constants were also impacted
by V8's introduction of ACCESSORS2, but do not need to be updated
the test:

- v8dbg_class_ThinString__actual__String changed in
  v8/v8@0f581e4

- v8dbg_class_UncompiledData__inferred_name__String changed in
  v8/v8@0f581e4

- v8dbg_class_JSFunction__shared__SharedFunctionInfo changed in
  v8/v8@8162090

- v8dbg_class_SharedFunctionInfo__function_data__Object had its
  accessor removed in
  v8/v8@a55803a
  This has been fixed in gen-postmortem-metadata.py.

PR-URL: #25852
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Author: cjihrig