[ADF-2859] conditional evaluation of disabled state for content actions (#3450)

* react on [disabled] binding changes

* [disabled] binding updates for context menu items

* evaluating disabled state with a function

* unit test

* restore original description

* remove irrelevant test

* fix tests

demo-shell/src/app/components/files/files.component.html

@@ -279,6 +279,12 @@
                 </data-columns>
 
                 <content-actions>
+                    <content-action
+                        target="all"
+                        title="Action for 'custom' node"
+                        [disabled]="isCustomActionDisabled"
+                        (execute)="runCustomAction($event)">
+                    </content-action>
                     <!-- Conditional actions demo -->
                     <content-action
                         icon="get_app"