Bit module in Core package

[raviqqe]

Close #670.

[codecov-commenter]

Codecov Report

Merging #673 (c420203) into main (2e92ae3) will decrease coverage by 0.01%.
The diff coverage is 12.50%.

@@            Coverage Diff             @@
##             main     #673      +/-   ##
==========================================
- Coverage   85.95%   85.93%   -0.02%     
==========================================
  Files         313      314       +1     
  Lines       28976    28983       +7     
==========================================
+ Hits        24905    24906       +1     
- Misses       4071     4077       +6     

Impacted Files	Coverage Δ
lib/core/ffi/src/bit.rs	0.00% <0.00%> (ø)
lib/core/ffi/src/lib.rs	100.00% <100.00%> (ø)
lib/ffi/src/closure.rs	100.00% <0.00%> (+3.22%)	⬆️

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