[Enhancement]: add generic type in metaclass

[csy1204]

Is there an existing issue for this?

• [X] I have searched the existing issues

What would you like to be added?

I would like to suggest an enhancement on typing SingleInstanceMetaClass

Why is this needed?

for development efficiency and code readability

Anything else?

Hello, I'm excited to start using Milvus and PyMilvus in our service. I'm committed to contributing to this awesome library.