Design doc:
https://docs.google.com/document/d/1ZU6rCvF2YHBGMLujWqqaxlPsjFfjKDE9C3-EugfdlAE/edit

Changes from the design doc:
- Changed to use 'class' declarations rather than 'type' declarations
  for things that need instance types but whose layout is not known to
  Torque. These declarations end with a semicolon rather than having a
  full set of methods and fields surrounded by {}. If the class's name
  should not be treated as a class name in generated output (because
  it's actually a template, or doesn't exist at all), we use the
  standard 'generates' clause to declare the most appropriate C++ class.
- Removed @instanceTypeName.
- @highestInstanceType became @highestInstanceTypeWithinParentClassRange
  to indicate a semantic change: it no longer denotes the highest
  instance type globally, but only within the range of values for its
  immediate parent class. This lets us use it for Oddball, which is
  expected to be the highest primitive type.
- Added new abstract classes JSCustomElementsObject and JSSpecialObject
  to help with some range checks.
- Added @lowestInstanceTypeWithinParentClassRange so we can move the new
  classes JSCustomElementsObject and JSSpecialObject to the beginning of
  the JSObject range. This seems like the least-brittle way to establish
  ranges that also include JSProxy (and these ranges are verified with
  static assertions in instance-type.h).
- Renamed @instanceTypeValue to @apiExposedInstanceTypeValue.
- Renamed @instanceTypeFlags to @reserveBitsInInstanceType.

This change introduces the new annotations and adds the ability for
Torque to assign instance types that satisfy those annotations. Torque
now emits two new macros:
- TORQUE_ASSIGNED_INSTANCE_TYPES, which is used to define the
  InstanceType enumeration
- TORQUE_ASSIGNED_INSTANCE_TYPE_LIST, which replaces the non-String
  parts of INSTANCE_TYPE_LIST

The design document mentions a couple of other macro lists that could
easily be replaced, but I'd like to defer those to a subsequent checkin
because this one is already pretty large.

Bug: v8:7793
Change-Id: Ie71d93a9d5b610e62be0ffa3bb36180c3357a6e8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1757094
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64258}