Remove use of Base.FastContiguousSubArray and pointer

[nhz2]

Base.FastContiguousSubArray is private, and Base.cconvert + Base.unsafe_convert is safer under potential future GC changes compared to the pointer function.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.39%. Comparing base (d49d569) to head (cd6d538).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #94   +/-   ##
=======================================
  Coverage   99.39%   99.39%           
=======================================
  Files           6        6           
  Lines         821      821           
=======================================
  Hits          816      816           
  Misses          5        5           

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