Implemented verifiers for the following classes:
- ExternalString
- FixedArrayBase
- JSCollection
- JSCollectionIterator
- JSWeakCollection
- Name
- SeqString
- Struct

Removed the following class definitions from Torque, because they're
just JSObject instances with particular starting maps, as discussed in
https://crrev.com/c/v8/v8/+/1619146/6/src/builtins/base.tq#459 :
- JSAccessorPropertyDescriptor
- JSDataPropertyDescriptor
- JSIteratorResult

Following similar logic, removed the Torque definition of
WasmExceptionPackage because it's just an error object that happens to
have a couple of private-symbol properties.

The following classes should not be defined in Torque because they're
just a starting state for JSObject, but I'm leaving them for now because
existing Torque code requires them:
- JSArgumentsObjectWithLength
- JSProxyRevocableResult

Bug: v8:9311
Change-Id: I0336b6be7d02e48e4a8a0f660e24d2c2fa5f5e34
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1637448
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61970}