Initializes the AEGIS-128x4 state with the provided key, nonce, and associated data.
The encryption key (must be aegis128x4_KEYBYTES long).
The nonce (must be aegis128x4_NPUBBYTES long).
The associated data (optional, can be empty).
AssertError if key or nonce lengths are invalid.
See Implementation
Initializes the AEGIS-128x4 state with the provided key, nonce, and associated data.