CI: mypy currently doesn't check numpy types

[tstadel]

Describe the bug
As we do not install numpy during our type-check CI step, numpy types like ndarray are not checked. If we install it however, several findings are shown:

mypy haystack
haystack/modeling/model/tokenization.py:432: error: Incompatible types in assignment (expression has type "List[str]", variable has type "ndarray[Any, dtype[Any]]")
haystack/modeling/data_handler/data_silo.py:749: error: Incompatible types in assignment (expression has type "ndarray[Any, dtype[Any]]", variable has type "List[int]")
haystack/modeling/data_handler/data_silo.py:765: error: No overload variant of "hstack" matches argument type "ndarray[Any, dtype[Any]]"
haystack/modeling/data_handler/data_silo.py:765: note: Possible overload variants:
haystack/modeling/data_handler/data_silo.py:765: note:     def [_SCT <: generic] hstack(tup: Sequence[Union[_SupportsArray[dtype[_SCT]], Sequence[_SupportsArray[dtype[_SCT]]], Sequence[Sequence[_SupportsArray[dtype[_SCT]]]], Sequence[Sequence[Sequence[_SupportsArray[dtype[_SCT]]]]], Sequence[Sequence[Sequence[Sequence[_SupportsArray[dtype[_SCT]]]]]]]]) -> ndarray[Any, dtype[_SCT]]
haystack/modeling/data_handler/data_silo.py:765: note:     def hstack(tup: Sequence[Union[_SupportsArray[dtype[Any]], _NestedSequence[_SupportsArray[dtype[Any]]], bool, int, float, complex, str, bytes, _NestedSequence[Union[bool, int, float, complex, str, bytes]]]]) -> ndarray[Any, dtype[Any]]
haystack/document_stores/memory.py:210: error: "ndarray[Any, Any]" has no attribute "unsqueeze"; maybe "squeeze"?
haystack/document_stores/memory.py:215: error: "ndarray[Any, dtype[Any]]" has no attribute "unsqueeze"; maybe "squeeze"?
haystack/document_stores/memory.py:231: error: "ndarray[Any, dtype[Any]]" has no attribute "to"
haystack/document_stores/memory.py:254: error: "ndarray[Any, dtype[Any]]" has no attribute "unsqueeze"; maybe "squeeze"?
haystack/pipelines/standard_pipelines.py:491: error: Argument "query_emb" to "query_by_embedding" of "BaseDocumentStore" has incompatible type "Optional[ndarray[Any, Any]]"; expected "ndarray[Any, Any]"
Found 8 errors in 4 files (checked 129 source files)

Expected behavior
numpy types are checked too and there are no mypy issues.

Additional context
Just checked the linux ci but windows ci should have the same issue.

To Reproduce

conda create -n mypy python=3.8
conda activate mypy
pip install mypy pydantic types-Markdown types-PyYAML types-requests types-setuptools types-six types-tabulate types-chardet types-emoji types-protobuf

# run mypy without numpy types
mypy haystack

# run mypy with numpy types
pip install numpy
mypy haystack

[ZanSara]

This happens for many other dependencies, pytorch being the worst offender along with transformers. We should find a way to tackle these issues progressively and clean up the repo of these errors.