Feature/rename into collection trait

[romaninsh]

I think that's a better name.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@a28a87c). Click here to learn what that means.
The diff coverage is 0%.

@@            Coverage Diff             @@
##             develop     #104   +/-   ##
==========================================
  Coverage           ?   98.77%           
  Complexity         ?      324           
==========================================
  Files              ?       16           
  Lines              ?      737           
  Branches           ?        0           
==========================================
  Hits               ?      728           
  Misses             ?        9           
  Partials           ?        0

Impacted Files	Coverage Δ	Complexity Δ
src/CollectionTrait.php	95.52% <0%> (ø)	25 <2> (?)

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