PYTHON-4297 Allow passing arbitrary index options to create_search_index

[ShaneHarvey]

https://jira.mongodb.org/browse/PYTHON-4297

[NoahStapp]

Do we want to remove this default?

[ShaneHarvey]

I'll ask that question in mongodb/specifications#1541.

[ShaneHarvey]

Updated to fix these typing failures:

pymongo/operations.py:591: error: Function is missing a type annotation for one
or more arguments  [no-untyped-def]
        def __init__(
        ^
pymongo/operations.py:615: error: Incompatible types in assignment (expression
has type "Mapping[str, Any]", target has type "str")  [assignment]
            self.__document["definition"] = definition
                                            ^
pymongo/operations.py:616: error: Incompatible types in assignment (expression
has type "Optional[str]", target has type "str")  [assignment]
            self.__document["type"] = type
                                      ^