feat: allow auditors to read template insights (#10860)

- Adds a template_insights pseudo-resource
- Grants auditor and template admin roles read access on template_insights
- Updates existing RBAC checks to check for read template_insights, falling back to template update permissions where necessary
- Updates TemplateLayout to show Insights tab if can read template_insights or can update template

coderd/rbac/object.go

@@ -193,6 +193,11 @@ var (
 	ResourceTailnetCoordinator = Object{
 		Type: "tailnet_coordinator",
 	}
+
+	// ResourceTemplateInsights is a pseudo-resource for reading template insights data.
+	ResourceTemplateInsights = Object{
+		Type: "template_insights",
+	}
 )
 
 // ResourceUserObject is a helper function to create a user object for authz checks.