using arc4random api as alternative backend for swoole_random_bytes,

[devnexen]

lessening file descriptor usage in the process too.

[codecov]

Codecov Report

Merging #4096 (5537aa4) into master (295e270) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4096      +/-   ##
==========================================
- Coverage   48.81%   48.76%   -0.06%     
==========================================
  Files          71       71              
  Lines       14269    14269              
==========================================
- Hits         6966     6958       -8     
- Misses       7303     7311       +8     

Impacted Files	Coverage Δ
src/core/base.cc	75.19% <ø> (ø)
src/os/async_thread.cc	67.98% <0.00%> (-2.20%)	⬇️
src/protocol/base.cc	61.18% <0.00%> (-1.98%)	⬇️

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