feat(alert): added isOpen input and marked as OnPush

[valorkin]

todo:

• add demo with switching dismissable property - DONE
• add demo with dynamic content with binding to outside of alert value - DONE

PR Checklist

Before creating new PR, please take a look at checklist below to make sure that you've done everything that needs to be done before we can merge it.

• read and followed the CONTRIBUTING.md guide.
• built and tested the changes locally.
• added/updated tests.
• added/updated API documentation.
• added/updated demos.

[YevheniiaMazur]

Demo looks good. Needs test fixing:

[codecov]

Codecov Report

Merging #2940 into development will increase coverage by 0.01%.
The diff coverage is 87.5%.

@@               Coverage Diff               @@
##           development    #2940      +/-   ##
===============================================
+ Coverage        65.78%   65.79%   +0.01%     
===============================================
  Files              207      207              
  Lines             5606     5608       +2     
  Branches           983      983              
===============================================
+ Hits              3688     3690       +2     
  Misses            1656     1656              
  Partials           262      262

Impacted Files	Coverage Δ
src/alert/alert.component.ts	89.65% <87.5%> (+0.76%)	⬆️

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[YevheniiaMazur]

Tested, looks good