[SIEM] Fix mocks for kibana context (#54996)

* Use our internal uiSettings mock in all context mocks

We were previously only using our internal uiSettings mock (which
returns real values) in our TestProviders component, as
all tests either needed:

* specific mocks, in which case we'd call jest.mock() ourselves
* broad mocks, for which platform's kibana_react mocks were usually
sufficient

However, a recent addition in the Timeline component added a usage of
uiSettings that could not use the default mock.

With this change, one can either jest.mock('lib/kibana') or use the
TestProviders wrapper to get real values for UI settings in test.

* Remove production code guarding against tests

This coalescence was due to the service not being properly mocked in
test, which is now fixed.

x-pack/legacy/plugins/siem/public/containers/timeline/index.tsx

@@ -81,8 +81,7 @@ class TimelineQueryComponent extends QueryTemplate<
       sourceId,
       sortField,
     } = this.props;
-    // I needed to do that to avoid test to yell at me since there is no good way yet to mock withKibana
-    const defaultKibanaIndex = kibana.services.uiSettings.get<string[]>(DEFAULT_INDEX_KEY) ?? [];
+    const defaultKibanaIndex = kibana.services.uiSettings.get<string[]>(DEFAULT_INDEX_KEY);
     const defaultIndex = isEmpty(indexPattern)
       ? [...defaultKibanaIndex, ...indexToAdd]
       : indexPattern?.title.split(',') ?? [];

x-pack/legacy/plugins/siem/public/mock/kibana_react.ts

@@ -71,7 +71,18 @@ export const createUseUiSetting$Mock = () => {
 };
 
 export const createUseKibanaMock = () => {
-  const services = { ...createKibanaCoreStartMock(), ...createKibanaPluginsStartMock() };
+  const core = createKibanaCoreStartMock();
+  const plugins = createKibanaPluginsStartMock();
+  const useUiSetting = createUseUiSettingMock();
+
+  const services = {
+    ...core,
+    ...plugins,
+    uiSettings: {
+      ...core.uiSettings,
+      get: useUiSetting,
+    },
+  };
 
   return () => ({ services });
 };
@@ -87,15 +98,11 @@ export const createWithKibanaMock = () => {
 
 export const createKibanaContextProviderMock = () => {
   const kibana = createUseKibanaMock()();
-  const uiSettings = {
-    ...kibana.services.uiSettings,
-    get: createUseUiSettingMock(),
-  };
 
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   return ({ services, ...rest }: any) =>
     React.createElement(KibanaContextProvider, {
       ...rest,
-      services: { ...kibana.services, uiSettings, ...services },
+      services: { ...kibana.services, ...services },
     });
 };