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.

test/v8-updates/test-postmortem-metadata.js

@@ -84,7 +84,7 @@ function getExpectedSymbols() {
     'v8dbg_class_Map__constructor_or_backpointer__Object',
     'v8dbg_class_Map__inobject_properties_start_or_constructor_function_index__char',
     'v8dbg_class_Map__instance_type__uint16_t',
-    'v8dbg_class_Map__instance_descriptors__DescriptorArray',
+    'v8dbg_class_Map__raw_instance_descriptors__DescriptorArray',
     'v8dbg_class_Map__instance_size_in_words__char',
     'v8dbg_class_Oddball__kind_offset__int',
     'v8dbg_class_Script__line_ends__Object',
@@ -116,8 +116,8 @@ function getExpectedSymbols() {
     'v8dbg_frametype_InternalFrame',
     'v8dbg_frametype_OptimizedFrame',
     'v8dbg_frametype_StubFrame',
-    'v8dbg_jsarray_buffer_was_neutered_mask',
-    'v8dbg_jsarray_buffer_was_neutered_shift',
+    'v8dbg_jsarray_buffer_was_detached_mask',
+    'v8dbg_jsarray_buffer_was_detached_shift',
     'v8dbg_namedictionary_prefix_start_index',
     'v8dbg_namedictionaryshape_entry_size',
     'v8dbg_namedictionaryshape_prefix_size',
@@ -134,7 +134,6 @@ function getExpectedSymbols() {
     'v8dbg_prop_desc_key',
     'v8dbg_prop_desc_size',
     'v8dbg_prop_desc_value',
-    'v8dbg_prop_idx_first',
     'v8dbg_prop_index_mask',
     'v8dbg_prop_index_shift',
     'v8dbg_prop_kind_mask',