keep full schema in cachew instead of just outer type

[karlicoss]

After recent google_takeout_parser update getting this:

...
  File "/home/hpi/.local/lib/python3.12/site-packages/cachew/marshall/cachew.py", line 143, in load
    tidx, val = dct
                └ 62.81359

TypeError: cannot unpack non-iterable float object

Seems that this is because we switched some PlaceVisit fields to Optional -- so now it tries to unpack a float as a Union (which Optional is a special case of).
Normally cachew would invalidate the cache in this case (since we keep the previous schema in the database)

cachew/src/cachew/__init__.py

Line 605 in 2abd77b

schema = str(self.cls_)

However seems that it is

 "schema": "typing.Union[google_takeout_parser.models.PlaceVisit, Exception]"`

, so if any of fields of PlaceVisit changed, this wouldn't have any impact.

I think we need to dump the datatype recursively in schema (with all field names etc -- doesn't hurt?) instead.

In the meantime for google_takeout_parser should be solvable by bumping google_takeout_version since it's also included in the cache key. cc @seanbreckenridge just in case you encounter this