This CL adds support for classes with methods.

More specifically:
- A new ValueSerializer is added and classes are serialized separetely
from functions, although the common parts are handled in the same way
and abstracted away.
- The function prototype is serialized as an object and any missing
information is set up again during deserialization.
- FunctionFlagsToFunctionKinds() is updated to allow for more function
kinds.
- Context serialization is updated to support serializing BlockContexts
and creating ScopeInfos of type CLASS_SCOPE.
- Map serialization is updated to support properties with custom
attributes.

Bug: v8:11525, v8:11706
Change-Id: I16ca7cbc17b1811721081cda05124ce36073f9be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3006416
Commit-Queue: Vicky Kontoura <vkont@google.com>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75893}