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

cypress/e2e/28-debug.cy.ts

@@ -126,6 +126,7 @@ describe('Debug', () => {
 		cy.url().should('not.include', '/debug');
 
 		workflowPage.actions.executeWorkflow();
+		workflowPage.actions.zoomToFit();
 		workflowPage.actions.deleteNode(IF_NODE_NAME);
 
 		executionsTab.actions.switchToExecutionsTab();