This patch is mostly mechanical. A few changes in
implementation-visitor.cc might be worth mentioning:
- Don't generate both field offset macros and class definitions for the
  same class. This was mostly just to keep me from forgetting to remove
  the DEFINE_FIELD_OFFSET_CONSTANTS part when converting classes, but
  also helpfully flagged that FixedArrayBase wasn't using the generated
  class that it requested.
- Generate forward declarations for all tq-defined classes in
  internal-class-definitions-tq.h. This is helpful for making things
  compile when classes have fields of other class types.
- When generating accessors for union types, use the nearest class type
  that contains the entire union rather than plain Object. This is
  important for compile-time type safety. It also required a few minor
  fixes elsewhere (isolate.cc, modules.cc, scope-info.cc,
  source-text-module.cc, and a correction of the field types in
  CallHandlerInfo to match how they're set in api.cc).

Change-Id: I3b9280e30779ce57fb9f3629eecfec898e26d708
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1774976Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#63458}