IgxComboBaseDirective: Refactor combo id setter

[ddaribo]

Related to #14305.

After discussion with @damyanpetev regarding this fix - #14414, the following changes in the IgxComboBaseDirective id setter are suggested:

1. Clear the selection set entry for the previous id.
2. Omit the lines closing the dropdown - this could be addressed on application level by setting the overlaySettings.oulet on the templated combos to the grid's outlet. Additionally logged an issue in igniteui-angular-samples to update the Cascading Combos sample with this.
3. Omit the blur of the combo input.