refactor: introduce clone helper for slice copying

[d-enk]

• Add clone() function that returns a shallow copy without preserving nilness
  is guaranteed to be inlined by the compiler (verified with -gcflags=-m)
  (separate from Clone() which preserves nilness - library convention is to return empty slice)
• Simplify Clone() to delegate to clone() for non-nil collections
• Refactor Chunk, Sliding, Drop, DropRight, DropWhile, DropRightWhile, Take, TakeWhile, Replace, Trim to use clone()
• Update SamplesBy and debounce.reset to use clone()
• Replace make(Slice, 0) with Slice{} for return statements

Also

• Some redundant checks have been removed in Take, NthOrEmpty
• Simplify TrimPrefix and TrimSuffix loops
• Micro-optimize Replace() by reordering condition to short-circuit on n != 0 first
  (TODO: consider adding early break when n reaches 0)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.27%. Comparing base (d610980) to head (d873409).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #784      +/-   ##
==========================================
+ Coverage   94.18%   94.27%   +0.08%     
==========================================
  Files          18       18              
  Lines        2873     2848      -25     
==========================================
- Hits         2706     2685      -21     
+ Misses        151      149       -2     
+ Partials       16       14       -2     

Flag	Coverage Δ
unittests	94.27% <100.00%> (+0.08%)	⬆️

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[d-enk]

Draft reason golang/go#77287