x.crypto.chacha20: makes 64-bit counter cipher works as an expected

[blackshirt]

This PR was motivated by discord disccussion here, especially, for firebird client testing by @einar-hjortdal with 64-bit counter chacha20 cipher that does not works as an expected previously. This patch was inspired from nakagami chacha20 used by golang firebird client in golang firebirdsql. Its adapted into existing x.crypto.chacha20 implementation.

This PR contains:

• Rewrites of xor_key_stream building block with the new one. Its splitted out keystream generation and xoring bytes into separated logic. Previously, its falls on the same keystream_with_blocksize routine. With this patch, key stream generation separated into Stream.keystream, focussing on keystream generation and updating internal counter, where xor-ing messages happens on xor_key_stream and or keystream_full helper.
• After this applied, the benchmark for xor_key_stream show a nice improvement, from ±53.430ms down into ±43.668ms. The benchmark also added into bench/bench.v file. It also make it more simpler and readable.
• Some bits of clean up: split out increasing internal counter into own routine in Stream.inc_ctr
• Marked a Cipher.reset method for deprecation. It intended for internal use, See some possibles culprits of this misbehaved calls tested by @tankf33der at here. Thanks to @tankf33der 👍
• Removes unnecessary codes

After this patch applied, in my testing for v firebird client with 64-bit counter activated, the tests was passed successfully. @einar-hjortdal: can you give it a try ?

Cheers,
thanks

[einar-hjortdal]

It seems to work well, good work!

[blackshirt]

It seems to work well, good work!

Glad to know its working for you. Thank you for testing it