Refactor performBatchUpdates implementation

[zenangst]

• Improve reliability of the perform batch updates method
• Don't invalidate when adding or inserting system views in FamilyScrollView

[codecov-io]

Codecov Report

Merging #208 (82f537f) into master (82be728) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #208   +/-   ##
=======================================
  Coverage   70.86%   70.86%           
=======================================
  Files           5        5           
  Lines         127      127           
=======================================
  Hits           90       90           
  Misses         37       37           

Flag	Coverage Δ
iOS	70.07% <ø> (ø)
macOS	56.69% <ø> (ø)
tvOS	33.85% <ø> (ø)

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