Provide backpressure on crypto binary

[akoshelev]

We've been reading from a file faster than we were encrypting. That caused sender buffer to grow infinitely.

[akoshelev]

I tested it locally and before this change, the memory used to encrypt 1M input was around 8Gb. After this change, I encrypted 30M and the memory usage stayed under 200Mb.

This change makes it a bit slower because once the channels are saturated, the producer (reading from a file) blocks on the first channel that is full while there may be others that are not full. Standard library does not expose channel size, so we would need to migrate to crossbeam if we want to do that

[eriktaubeneck]

ship it!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.28%. Comparing base (e7a234a) to head (ff65340).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1486      +/-   ##
==========================================
- Coverage   93.28%   93.28%   -0.01%     
==========================================
  Files         239      239              
  Lines       43532    43532              
==========================================
- Hits        40608    40607       -1     
- Misses       2924     2925       +1     

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