web: fix event propagation in search-select wrappers (#8224)

web: fix event propogation in search-select wrappers

Two different patches, an older one that extracted long search
blocks that were cut-and-pasted into a standalone component, and a
newer one that fixed displaying placeholder values properly,
conflicted and broke a relationship that allowed for the values to
be propagated through those standalone components correctly.

This restores the event handling and updates the listener set-ups
with more idiomatic hooks into Lit's event system.

web/src/admin/common/ak-flow-search/FlowSearch.ts

@@ -74,7 +74,6 @@ export class FlowSearch<T extends Flow> extends CustomListenerElement(AKElement)
         this.fetchObjects = this.fetchObjects.bind(this);
         this.selected = this.selected.bind(this);
         this.handleSearchUpdate = this.handleSearchUpdate.bind(this);
-        this.addCustomListener("ak-change", this.handleSearchUpdate);
     }
 
     handleSearchUpdate(ev: CustomEvent) {
@@ -124,6 +123,7 @@ export class FlowSearch<T extends Flow> extends CustomListenerElement(AKElement)
                 .renderDescription=${renderDescription}
                 .value=${getFlowValue}
                 .name=${this.name}
+                @ak-change=${this.handleSearchUpdate}
                 ?blankable=${!this.required}
             >
             </ak-search-select>