[blackshirt]

This PR enables partial support for creating ChaCha20 cipher with 64-bit counter, see (#23904) issues about this features requested. I call its a partial support, because not all functionality was availables for 64-bit counter variant of ChaCha20 ciphers for current time of writing, especially for xor_key_stream, it still need to be looked again. The .encrypt method was tested working with this new variant of cipher. I am having difficulty finding trusted sources that can be used as references.

With this PR merged, its possible to create new variant of ChaCha20 stream cipher with 64-bit counter, by providing 8-bytes length of nonce into new_cipher routine.
The test has been added with samples of data generates from modified ptyhon script.

Updates:

I have add a test for xor_key_stream behaviour for ChaCha20 cipher with 64-bit counter
The golang script to produce verified output was included in the comments of the test files.

Thanks

[huly-for-github]

Connected to Huly®: V_0.6-22444

[blackshirt]

Thanks for merging it. There are several areas that can be improved later. I think its solid enough for now, i will left it as is, and continues my other work..
Good days