Update formControlHasFocus asynchronously

[Blackbaud-PaulCrowder]

This fixes an issue where components inside an input box (like the phone field) manipulate the focused element, leading to an ExpressionChangedAfterItHasBeenCheckedError.

[blackbaud-ado]

Preview build at https://host.nxt.blackbaud.com/skyux-forms?_sp.spa=pr-input-box-focus-style-delay

[codecov]

Codecov Report

Merging #208 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #208   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           29        29           
  Lines          866       869    +3     
  Branches       164       164           
=========================================
+ Hits           866       869    +3     

Impacted Files	Coverage Δ
...pp/public/modules/input-box/input-box.component.ts	100.00% <100.00%> (ø)

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