Add schema support for pyarrow map / struct / dictionary type

lancedb API throws TypeError: Converting Pydantic type to Arrow Type: unsupported type typing.Dict[str, str]. ( same for Dict[int,str] ) . Issue is in lance not supporting the pyarrow map types.

To Reproduce :

from lancedb.pydantic import Vector, LanceModel, Dict

class Content(LanceModel):
    id: int
    vector: Vector(1)
    metadata: Dict[int, str]

db = lancedb.connect("./lancedb")
tbl = db.create_table("test", schema=Content.to_arrow_schema())

Start by reproducing the example through LanceModel.to_arrow_schema() with Dict[str, str] and Dict[int, str]. Trace the schema conversion path for the unsupported PyArrow map, struct, and dictionary types; done means these declarations produce a valid Arrow schema and the create_table example succeeds.