Revert recent changes in cpp_int/bitwise

[ckormanyos]

The purpose of this PR is to revert recent changes in cpp_int/bitwise.hpp in order to see if these are the cause of the undefined behavior detections in an unrelated Math PR.

Cc: @mborland and @jzmaddock

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.1%. Comparing base (9de48c7) to head (ccdaf10).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #689     +/-   ##
=========================================
- Coverage     94.1%   94.1%   -0.0%     
=========================================
  Files          280     280             
  Lines        29074   29074             
=========================================
- Hits         27349   27347      -2     
- Misses        1725    1727      +2     

Files with missing lines	Coverage Δ
include/boost/multiprecision/cpp_int/bitwise.hpp	85.2% <100.0%> (ø)

... and 1 file with indirect coverage changes

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[ckormanyos]

Closing since this is not needed