refactor: replace verify_interface with isinstance

[josecorella]

Issue #, if available:
#464

Description of changes:

1. pyca/cryptography is planning to remove verify_interface. However; since they run the esdk as downstream in ci, they can't deprecate the function without breaking their CI. This PR is intended to unblock them by removing verify_interface from the ESDK. verify_interface takes an abstract class in this case ec.EllipticCurve and the subclass object you wish to verify, in our use case it's algorithm.signing_algorithm_info which is a subclass that implements the ec.EllipticCurve abstract class. The only allowed subclasses we use are ec.SECP256R1 and ec.SECP384R1 and verify_interface goes through the class and makes sure that the expected values are there. Since both of the allowed subclasses implement ec.EllipticCurve, using isinstance works as a replacement.

2. I noticed that the test_vector_handlers static analysis action is failing because of linter dependency issues. I went ahead and updated it to use the pinned dependencies in dev_requirements/. If these changes don't make sense to include in the same PR I am happy to break them up into two :)

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[texastony]

Looks good. Left a nit.
I am going to dig into what verify_interface actually does...
Is there a reason we originally used verify_interface instead of isinstance?
Did @josecorella look into this?
If so, can you update the PR's description to mention your findings?

UPDATE: I had not realized that pyca had already suggested to us that isinstance offers the same guarantees, at least in our use cases.

[texastony]

nit: remove left over commented out code

[nicolas-velazquez-koin]

Hi! Due to this refactor an error NotSupportedError("Unsupported signing algorithm info") is raised when decrypting with some Algorithms with version of cryptography=2.8. I upgrade the cryptography version to the latest (41.0.7 right now) and the error was gone. I dont know from what version the issue is resolved.

I suggest to increase the required version of cryptography in your guide.

Algorithm with issue: AlgorithmSuite.AES_256_GCM_HKDF_SHA512_COMMIT_KEY_ECDSA_P384

Error log:
Error on closing
Traceback (most recent call last):
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/init.py", line 196, in decrypt
plaintext = decryptor.read()
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/streaming_client.py", line 260, in read
self._prep_message()
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/streaming_client.py", line 792, in _prep_message
self._header, self.header_auth = self._read_header()
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/streaming_client.py", line 830, in _read_header
decryption_materials = self.config.materials_manager.decrypt_materials(request=decrypt_materials_request)
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/materials_managers/caching.py", line 251, in decrypt_materials
new_result = self.backing_materials_manager.decrypt_materials(request)
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/materials_managers/default.py", line 155, in decrypt_materials
verification_key = self._load_verification_key_from_encryption_context(
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/materials_managers/default.py", line 136, in _load_verification_key_from_encryption_context
verifier = Verifier.from_encoded_point(algorithm=algorithm, encoded_point=encoded_verification_key)
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/internal/crypto/authentication.py", line 144, in from_encoded_point
return cls(
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/internal/crypto/authentication.py", line 44, in init
self._signature_type = self._set_signature_type()
File "/.local/lib/python3.8/site-packages/aws_encryption_sdk/internal/crypto/authentication.py", line 51, in _set_signature_type
raise NotSupportedError("Unsupported signing algorithm info")
aws_encryption_sdk.exceptions.NotSupportedError: Unsupported signing algorithm info