Wrapped components getter refactor

[mdelez]

After discussing with Tobias, we think that the getter method in a wrapped component should only check the validity of the form if possible instead of checking each FormControl for specific criteria since the form will be valid if all the criteria is met. We should make this change on all of the wrapped components.

Old method
https://github.com/dasch-swiss/knora-ui-ng-lib/blob/43ee1e8697784eea36cd1de0fb3d012e5d8d25a8/projects/knora-ui/src/lib/viewer/values/time-value/time-input/time-input.component.ts#L123-L129

New method
https://github.com/dasch-swiss/knora-ui-ng-lib/blob/692226bd8d9d5a93e5d78d68fe69254a45796a68/projects/knora-ui/src/lib/viewer/values/time-value/time-input/time-input.component.ts#L123-L129

[tobiasschweizer]

I will submit a related PR for angular/components#18817

[tobiasschweizer]

Angular custom form field example fixed in angular/components#18844

[mdelez]

That was quick :) good work!

[tobiasschweizer]

I am not bright but quick ;-)