json-serde: streaming md5

[mateusz834]

(for canada 100)

Before:

User time (seconds): 3.61
Maximum resident set size (kbytes): 542020

After:

User time (seconds): 3.45
Maximum resident set size (kbytes): 114816

[hanabi1224]

Thanks for the PR! It's a great optimization, but I think it makes the zig solution incomparable to others, I might need more time to think about it.

[mateusz834]

How about 2-streaming.zig ? I also added streaming md5 for go and rust. (go doesn't have any performance improvements, it buffers the entire json before writing) and added error handling for the go code.