API updates:

- Mac class follows hashlib API: digest functions added and finalization no longer modifies state.
- Encryptor and Decryptor now raise RuntimeError if still used after final.

Documentation updated with the changes and  further examples.

Tests updated with the changes, new test module for error cases (test_raises).

Docstrings improved.

pyaegis/benchmark.py

@@ -57,14 +57,14 @@ def bench_mac(ciph) -> None:
     buf = bytearray(MSG_LEN)
     buf[:] = _random_bytes(len(buf))
 
-    mac0 = ciph.Mac(key, nonce)
+    mac0 = ciph.Mac(key, nonce, maclen=ciph.MACBYTES_LONG)
     mac_out = bytearray(ciph.MACBYTES_LONG)
 
     t0 = time.perf_counter()
     for _ in range(ITERATIONS):
         mac = mac0.clone()
         mac.update(buf)
-        mac.final(maclen=ciph.MACBYTES_LONG, into=mac_out)
+        mac.final(into=mac_out)
     t1 = time.perf_counter()
 
     _ = mac_out[0]