Python code cleanup

These changes should not change any functionality.

In code:

- Added async keyword to CryptoSystem::kind since it's actually implemented async
- Removed unused socket import in json_api

In tests:
- Removed unused imports
- Removed unnecessary return statements
- Removed unused variables
- Cleaned up some spacing to match PEP-8
- Changed many comparisons to match PEP-8
- Use ValueSubKey classes instead of integers to keep types in line

veilid-python/tests/test_crypto.py

@@ -3,7 +3,6 @@
 import pytest
 import veilid
 from veilid.api import CryptoSystem
-import gc
 
 
 @pytest.mark.asyncio
@@ -42,9 +41,10 @@ async def test_hash_and_verify_password(api_connection: veilid.VeilidAPI):
         assert await cs.verify_password(b"abc123", phash)
 
         # Password mismatch
-        phash2 = await cs.hash_password(b"abc1234", salt)
+        await cs.hash_password(b"abc1234", salt)
         assert not await cs.verify_password(b"abc12345", phash)
 
+
 @pytest.mark.asyncio
 async def test_sign_and_verify_signature(api_connection: veilid.VeilidAPI):
     cs = await api_connection.best_crypto_system()