This annotation indicates that the class itself is not instantiated,
and does not have its own instance type: The instance types that
logically belong to the class are the instance types of the derived
classes.

Currently, we need the indication @dirtyInstantiatedAbstractClass
for several classes that are used as both, abstract base classes
and concrete classes. The prime example is JSObject which is the
base for many other classes, and also serves as the class to allocate
plain JSObjects. The annotation is purposefully ugly because in the
future we should refactor code to make it unnecessary.

Another annotation we introduce is @hasSameInstanceTypeAsParent,
which indicates another design pattern that currently occurs in the
code-base: Some Torque classes have the same instance types as their
parent class, but rename some fields, or possibly have a different map.
In such cases, the parent class is not abstract and the derived classes
can be seen as refinements of this class (that, for example, narrows the
type of a field). In the future, Torque should accomodate this pattern
better, but at moment we are content with just indicating where it is
used.

Bug: v8:7793
Change-Id: I1892dcc7325250df75d80308bf3d767d6d43bcc2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1607761
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61495}