[python] Remove the no-longer-needed wrapper layers

[johnkerl]

Tracks PPR #3209

The wrapper layers were useful during the cppification project -- they allowed us to migrate from tiledb-py-backed classes to libtiledbsoma-backed classes.

At this point, however, they simply add to the keystroking on all Python dev work. It's time to get rid of them, to save us all from needless copypasta in our development work moving forward.