[EuiProviders] Warn Developer if EuiProvider is missing (#184608)

## Summary

Addresses elastic/kibana-team#805

## Rollout plan

These steps will graduate toward a consistency of Dark Mode theming (and
I18n, and Analytics for Error Boundaries) by ensuring that EUI
components are always rendered with `KibanaRenderContextProvider`
wrapping the root of the rendering tree.

**The final behavior:** in Dev mode when KibanaRenderContextProvider is
missing, developers will see a console.error and a toast Error message.
In CI environments, the error scenario will cause the EUI components to
fail with an error and developers will have to address the issue with a
fix by viewing the test logs.

1. **[Done]** Initial error behavior: throw error if EUI Provider is
missing in a Draft PR. In CI of that Draft PR, EUI components will fail
to render and show an error.
1. SharedUX team (@tsullivan) implements the fixes using separate PRs
2. **[In this PR]** Soften the error behavior and take effect only in
Dev mode
    1. Use console.error to give an error message and a stack trace
    2. Show an Error toast to convey the error message to Developers
3. **[Not Started]** ~~After running in a mode of step 2 for a length of
time, we add restrictions to CI environments with the final error
behavior.~~ Update the navigation methods of the common page objects for
functional tests, to detect when the toast message appears during
functional testing, and throw a helpful error.

## Notification for developers
Developers would see this error toast with a message telling them they
need to use EuiProvider, plus a link for "more details." They can also
check the JS console to see the error details.

<img width="1798" alt="image"
src="https://github.com/elastic/kibana/assets/908371/061fcec8-4a66-45fd-a77a-c6a2226f7871">

## How this helps
Surfacing these kinds of errors automates the discovery of finding where
dark mode issues exist. Here is an example of a hard-to-find dark mode
issue that was easily caught by the kinds of testing enabled in this PR:

<img width="1436" alt="connection details - before"
src="https://github.com/elastic/kibana/assets/908371/ec6c19b0-5697-41bd-a8eb-935e8388983d">

The way to problems in this nature is to wrap the React context in
`<KibanaRenderContextProvider>`, and setting the required CoreStart
service dependencies of `analytics`, `i18n` and `theme`.

packages/core/chrome/core-chrome-browser-internal/src/chrome_service.tsx

@@ -11,6 +11,7 @@ import { FormattedMessage } from '@kbn/i18n-react';
 import { BehaviorSubject, combineLatest, merge, type Observable, of, ReplaySubject } from 'rxjs';
 import { mergeMap, map, takeUntil, filter } from 'rxjs';
 import { parse } from 'url';
+import { setEuiDevProviderWarning } from '@elastic/eui';
 import useObservable from 'react-use/lib/useObservable';
 
 import type { CoreContext } from '@kbn/core-base-browser-internal';
@@ -173,6 +174,39 @@ export class ChromeService {
     this.mutationObserver.observe(body, { attributes: true });
   };
 
+  // Ensure developers are notified if working in a context that lacks the EUI Provider.
+  private handleEuiDevProviderWarning = (notifications: NotificationsStart) => {
+    const isDev = this.params.coreContext.env.mode.name === 'development';
+    if (isDev) {
+      setEuiDevProviderWarning((providerError) => {
+        const errorObject = new Error(providerError.toString());
+        // show a stack trace in the console
+        // eslint-disable-next-line no-console
+        console.error(errorObject);
+
+        notifications.toasts.addDanger({
+          title: '`EuiProvider` is missing',
+          text: mountReactNode(
+            <p data-test-sub="core-chrome-euiDevProviderWarning-toast">
+              <FormattedMessage
+                id="core.chrome.euiDevProviderWarning"
+                defaultMessage="Kibana components must be wrapped in a React Context provider for full functionality and proper theming support. See {link}."
+                values={{
+                  link: (
+                    <a href="https://docs.elastic.dev/kibana-dev-docs/react-context">
+                      https://docs.elastic.dev/kibana-dev-docs/react-context
+                    </a>
+                  ),
+                }}
+              />
+            </p>
+          ),
+          toastLifeTimeMs: 60 * 60 * 1000, // keep message visible for up to an hour
+        });
+      });
+    }
+  };
+
   public setup({ analytics }: SetupDeps) {
     const docTitle = this.docTitle.setup({ document: window.document });
     registerAnalyticsContextProvider(analytics, docTitle.title$);
@@ -188,6 +222,7 @@ export class ChromeService {
   }: StartDeps): Promise<InternalChromeStart> {
     this.initVisibility(application);
     this.handleEuiFullScreenChanges();
+    this.handleEuiDevProviderWarning(notifications);
 
     const globalHelpExtensionMenuLinks$ = new BehaviorSubject<ChromeGlobalHelpExtensionMenuLink[]>(
       []