Refactor UICollectionViewController support

[zenangst]

• Use addSubview rather than insertSubview(at:) to fix issue with navigation bars not collapsing properly
• Disable user interactions and set background color to clear on internal collection view controllers wrapper view.

[codecov-commenter]

Codecov Report

Merging #196 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #196   +/-   ##
=======================================
  Coverage   81.45%   81.45%           
=======================================
  Files          11       11           
  Lines         836      836           
=======================================
  Hits          681      681           
  Misses        155      155           

Flag	Coverage Δ
#iOS	84.00% <ø> (ø)
#macOS	80.14% <ø> (ø)
#tvOS	43.00% <ø> (ø)

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