Add pytest to the github workflow.

[rbair23]

I had problems with two type annotations that failed to compile. I removed these in this change, and we can (and should) add them back in when we have a solution.

[rbair23]

I had to remove the type definitions for public_key and private_key init methods because of this error:

➜  hiero-sdk-python git:(00047-CI-PyTest) ✗ uv run pytest
ImportError while loading conftest '/Users/richardbair/Projects/hiero/hiero-sdk-python/tests/conftest.py'.
tests/conftest.py:3: in <module>
    from hiero_sdk_python.account.account_id import AccountId
src/hiero_sdk_python/__init__.py:10: in <module>
    from .crypto.private_key import PrivateKey
src/hiero_sdk_python/crypto/private_key.py:7: in <module>
    class PrivateKey:
src/hiero_sdk_python/crypto/private_key.py:12: in PrivateKey
    def __init__(self, private_key: ec.EllipticCurvePrivateKey | ed25519.Ed25519PrivateKey):
E   TypeError: unsupported operand type(s) for |: 'ABCMeta' and 'ABCMeta'