Update pydantic samples to use contrib module

[dandavison]

To merge once temporalio/sdk-python#757 is released

[cretz]

Would prefer a pydantic_converter_v1 sample instead of putting inside another sample

[dandavison]

v1's a thing of the past. I think that pollutes the top-level namespace unnecessarily.

[cretz]

I think it's easier to ignore a top-level sample you don't care about than code inside a sample you do. This looks like v1 is a subdir/module of the pydantic_converter sample, not its own sample. Subdirs of Python code are usually considered modules of that code, not separate/unrelated (and this has been the case in samples thus far).

[dandavison]

OK you're probably right about the structure. But let's delete it at some point -- when we do we can always leave a permalink to the content in git history in the remaining README of the v2 sample.

[cretz]

Would move this to tests/pydantic_converter_v1 dir