Add other input types for SQLAlchemy BIT model

[jackrua]

Hi,

First of all, thank you for the great library @ankane!

I'm opening this PR to address some issues that have been raised by users (#84, #110 and #112), that is to input types other than string in the BIT SQLAlchemy model (also when using the asyncpg dialect). In brief with this PR, given:

class Item(Base):
id = mapped_column(Integer, primary_key=True)
binary_embedding = mapped_column(BIT(3))

You can add it to your database using whatever input you like (and this will be transformed following the logic already present in the init of the Bit class):

with Session(engine) as session: session.add(Item(id = 1, binary_embedding = [True, False, True])) # or [1, 0, 1], or np.array([1, 0, 1]) 

[ankane]

Hi @jackrua, thanks for the PR. Added support for passing str objects in the commit above. I think the other changes are breaking to some degree, but may make sense for 0.5.0.

[jackrua]

Thank you @ankane for the feedback and sorry for the late response. I merged master in my branch and updated my PR, and now the CI passes too.

However, I was thinking that now when you read from the DB using the sqlalchemy model, we are returning str in some cases and BitString in others, wouldn't it be better to always return a Bit object (similar to what you do with HALFVEC for example), what do you think?
I wanted to implement the result_processor method to fix this in this PR but I wasn't sure what you thought about it, let me know.