perf(editor): Improve performance when opening large workflows with node issues (#7901)

This PR should improve performance when opening large workflows that
contain node issues (Fixes ADO-1521)

**Background**
Main reason for this poor performance is that our `getCurrentWorkflow()`
store getter is unnecessarily heavy but on top of that we are calling it
more than we need. This addresses the second part of the issue by
changing the following:
- Pausing node issue processing while workflows are loading
- Only getting current workflow once (instead for every node) when
calling `refreshNodeIssues`

**Benchmark**
This was tested on a workflow attached to [this Linear
ticket](https://linear.app/n8n/issue/ADO-1501/deliveryhero-enterprise-instance-very-slow-loading-workflows)
and this fix brings down opening time from **~1m10s** to **~28s** on my
laptop.

**Tests**
- [Latest e2e tests
run](https://github.com/n8n-io/n8n/actions/runs/7060874994)

https://community.n8n.io/t/ui-very-slow-with-more-than-100-nodes/8236/14

packages/editor-ui/src/views/NodeView.vue

@@ -692,6 +692,9 @@ export default defineComponent({
 		instance(): BrowserJsPlumbInstance {
 			return this.canvasStore.jsPlumbInstance;
 		},
+		isLoading(): boolean {
+			return this.loadingService !== null;
+		},
 		currentWorkflowObject(): Workflow {
 			return this.workflowsStore.getCurrentWorkflow();
 		},
@@ -2697,10 +2700,6 @@ export default defineComponent({
 
 				this.dropPrevented = true;
 				this.workflowsStore.addConnection({ connection: connectionData });
-				this.uiStore.stateIsDirty = true;
-				if (!this.suspendRecordingDetachedConnections) {
-					this.historyStore.pushCommandToUndo(new AddConnectionCommand(connectionData));
-				}
 
 				if (!this.isReadOnlyRoute && !this.readOnlyEnv) {
 					NodeViewUtils.hideOutputNameLabel(info.sourceEndpoint);
@@ -2742,8 +2741,14 @@ export default defineComponent({
 					}
 				}
 				this.dropPrevented = false;
-				this.updateNodesInputIssues();
-				this.resetEndpointsErrors();
+				if (!this.isLoading) {
+					this.uiStore.stateIsDirty = true;
+					if (!this.suspendRecordingDetachedConnections) {
+						this.historyStore.pushCommandToUndo(new AddConnectionCommand(connectionData));
+					}
+					this.updateNodesInputIssues();
+					this.resetEndpointsErrors();
+				}
 			} catch (e) {
 				console.error(e);
 			}