Optimisation - Array intersection over selection

[luke-hill]

Ran a quick fast-ruby style optimisation check. For the code here: https://github.com/site-prism/site_prism-all_there/blob/main/lib/site_prism/all_there/expected_items.rb#L68

Warming up --------------------------------------
array select and include 
                        21.776k i/100ms
  array intersection    74.987k i/100ms
Calculating -------------------------------------
array select and include
                        220.481k (± 3.4%) i/s -      1.111M in   5.043750s
  array intersection    741.762k (± 3.6%) i/s -      3.749M in   5.062687s

Comparison:
  array intersection:   741761.5 i/s
array select and include:   220480.7 i/s - 3.36x  slower