move daft.daft.spark_connect into a dedicated module

[universalmind303]

Is your feature request related to a problem?

currently the spark_connect function is exported directly from our "private" daft.daft module. This should instead be reexported through a dedicated module.

Describe the solution you'd like

instead of

from daft.daft import spark_connect

we should instead do something like this:

from daft.spark import spark_connect

Describe alternatives you've considered

No response

Additional Context

No response

Would you like to implement a fix?

No