perf: reduce overhead of various methods

[faustbrian]

Summary

• Migrate some fast.js methods over and remove unnecessary functionality.
• Remove the ability to pass strings as iteratees, always expect a function.

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@94ec7ef). Click here to learn what that means.
The diff coverage is 100%.

@@           Coverage Diff           @@
##             master    #31   +/-   ##
=======================================
  Coverage          ?   100%           
=======================================
  Files             ?    142           
  Lines             ?    786           
  Branches          ?     91           
=======================================
  Hits              ?    786           
  Misses            ?      0           
  Partials          ?      0

Impacted Files	Coverage Δ
src/pull-all.ts	100% <100%> (ø)
src/uniq-by.ts	100% <100%> (ø)
src/index.ts	100% <100%> (ø)
src/internal/compound-words.ts	100% <100%> (ø)
src/key-by.ts	100% <100%> (ø)
src/reduce.ts	100% <100%> (ø)
src/map-values.ts	100% <100%> (ø)
src/map-object.ts	100% <100%> (ø)
src/reduce-right-array.ts	100% <100%> (ø)
src/pluck.ts	100% <100%> (ø)
... and 33 more

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