title: Angular Formly: HideExpression does not kick in on page load (Angular 10)
body: <p><strong>Facing this issue in Angular 10</strong></p>
  <p>I have a number of fields on my form. When the user changes the selected value in a dropdown, there is a <code>hideExpression</code> on each field that shows/hides the fields depending on what the user has selected. This currently works fine.</p>
  <p>However, I am trying to make the dropdown default to the first option in the select. This also works fine.</p>
  <p>My issue is that all of the <code>hideExpression</code> logic is not being fired upon loading of the screen. So the select is defaulting correctly but none of the fields (that should be shown) that go with that option are visible.
  If I manually change the dropdown value then everything is shown correctly. Is there a way to make the <code>hideExpression</code> logic get kicked off even when the select is being defaulted via code?</p>
  <p>The page defaults to Option2. Yet, there is a hidden field that should show whenever Option2 is selected. So if you change the dropdown to Option1 and then back to Option2...you will see the hidden field. The hide/show logic doesn't seem to get kicked off if you set a dropdown to a certain value by default.</p>
  <p><em><strong>Note</strong></em>
  <em>The code is little complicated, so I can't replicate it in a Plunkr</em></p>