fix: chacha circuit

[lonerapier]

fixes AES and ChaCha circuit ciphertext check by only checking till plaintext length and not beyond.

• for AES, uses IsEqualArrayPaddedLHS template to only check for non-padded parts in an array

• for CHACHA, passes a new input signal length and check only till that index

• Closes feat: preferable to have chacha take in bytes instead of bits.  #58

[lonerapier]

another path to prevent this constraint blowup could be to leave this as it is, and compute ciphertext again outside the circuit. the original ciphertext should remain unchanged when computed for padded plaintext, so shouldn't create any security issues. But definitely need more discussion, if it's the right path.

[Autoparallel]

looks good, will merge when all ci passes