[UI Errors] Change errorType label to error_type (#224668)

## Summary

When checking the Overview cluster, I noticed that we previously had
`labels.error_type` in APM. In this PR, I changed the label that I've
added in the following PRs for fatal react errors and toast errors to
use `labels.error_type` instead of `labels.errorType` for consistency.

- Toast error: https://github.com/elastic/kibana/pull/217948
- Fatal react error: https://github.com/elastic/kibana/pull/218846

src/core/packages/notifications/browser-internal/src/toasts/toasts_api.test.ts

@@ -215,7 +215,7 @@ describe('#addDanger()', () => {
     const toasts = new ToastsApi(toastDeps());
     expect(toasts.addDanger({})).toHaveProperty('color', 'danger');
     expect(apm.captureError).toBeCalledWith('No title or text is provided.', {
-      labels: { errorType: 'ToastDanger' },
+      labels: { error_type: 'ToastDanger' },
     });
   });
 
@@ -225,7 +225,7 @@ describe('#addDanger()', () => {
     const currentToasts = await getCurrentToasts(toasts);
     expect(currentToasts[0]).toBe(toast);
     expect(apm.captureError).toBeCalledWith('No title or text is provided.', {
-      labels: { errorType: 'ToastDanger' },
+      labels: { error_type: 'ToastDanger' },
     });
   });
 
@@ -234,7 +234,7 @@ describe('#addDanger()', () => {
     const toast = toasts.addDanger({ title: 'foo', toastLifeTimeMs: undefined });
     expect(toast.toastLifeTimeMs).toEqual(10000);
     expect(apm.captureError).toBeCalledWith('foo', {
-      labels: { errorType: 'ToastDanger' },
+      labels: { error_type: 'ToastDanger' },
     });
   });
 });
@@ -248,7 +248,7 @@ describe('#addError', () => {
     expect(toast).toHaveProperty('color', 'danger');
     expect(toast).toHaveProperty('title', 'Something went wrong');
     expect(apm.captureError).toBeCalledWith(error, {
-      labels: { errorType: 'ToastError' },
+      labels: { error_type: 'ToastError' },
     });
   });
 
@@ -260,7 +260,7 @@ describe('#addError', () => {
     const currentToasts = await getCurrentToasts(toasts);
     expect(currentToasts[0]).toBe(toast);
     expect(apm.captureError).toBeCalledWith(error, {
-      labels: { errorType: 'ToastError' },
+      labels: { error_type: 'ToastError' },
     });
   });
 });

src/core/packages/notifications/browser-internal/src/toasts/toasts_api.tsx

@@ -49,7 +49,7 @@ const getToastTitleOrText = (toastOrTitle: ToastInput): string => {
 
 const getApmLabels = (errorType: 'ToastError' | 'ToastDanger') => {
   return {
-    errorType,
+    error_type: errorType,
   };
 };
 

src/platform/packages/shared/shared-ux/error_boundary/lib/error_boundary_labels.ts

@@ -11,6 +11,6 @@ export const getErrorBoundaryLabels = (
   errorType: 'PageFatalReactError' | 'SectionFatalReactError'
 ) => {
   return {
-    errorType,
+    error_type: errorType,
   };
 };

src/platform/packages/shared/shared-ux/error_boundary/src/ui/error_boundary.test.tsx

@@ -135,7 +135,7 @@ describe('<KibanaErrorBoundary>', () => {
     expect(apm.captureError).toHaveBeenCalledTimes(1);
     expect(apm.captureError).toHaveBeenCalledWith(
       new Error('This is an error to show the test user!'),
-      { labels: { errorType: 'PageFatalReactError' } }
+      { labels: { error_type: 'PageFatalReactError' } }
     );
   });
 });

src/platform/packages/shared/shared-ux/error_boundary/src/ui/section_error_boundary.test.tsx

@@ -131,7 +131,7 @@ describe('<KibanaSectionErrorBoundary>', () => {
     expect(apm.captureError).toHaveBeenCalledTimes(1);
     expect(apm.captureError).toHaveBeenCalledWith(
       new Error('This is an error to show the test user!'),
-      { labels: { errorType: 'SectionFatalReactError' } }
+      { labels: { error_type: 'SectionFatalReactError' } }
     );
   });
 });