[SIEM] Add tooltip to Host/Network Anomalies Tables (#41173)

## Summary

As discussed in the weekly SIEM Sync, adding a tooltip to the Anomalies Tables clarifying that results are not constrained by filters in the global KQL bar.

<img src="https://user-images.githubusercontent.com/2946766/61242979-3efd3480-a704-11e9-86f7-62e6c75f6654.png" width=300>



### Checklist

Use ~~strikethroughs~~ to remove checklist items you don't feel are applicable to this PR.

- [x] This was checked for cross-browser compatibility, [including a check against IE11](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility)
- [x] Any text added follows [EUI's writing guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses sentence case text and includes [i18n support](https://github.com/elastic/kibana/blob/master/packages/kbn-i18n/README.md)
- [ ] ~[Documentation](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#writing-documentation) was added for features that require explanation or tutorials~
- [ ] ~[Unit or functional tests](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility) were updated or added to match the most common scenarios~
- [ ] ~This was checked for [keyboard-only and screenreader accessibility](https://developer.mozilla.org/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Accessibility#Accessibility_testing_checklist)~

### For maintainers

- [ ] ~This was checked for breaking API changes and was [labeled appropriately](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#release-notes-process)~
- [ ] ~This includes a feature addition or change that requires a release note and was [labeled appropriately](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#release-notes-process)~

x-pack/legacy/plugins/siem/public/components/ml/tables/anomalies_host_table.tsx

@@ -78,6 +78,7 @@ export const AnomaliesHostTable = React.memo<AnomaliesHostTableProps>(
             <HeaderPanel
               subtitle={`${i18n.SHOWING}: ${hosts.length.toLocaleString()} ${i18n.ANOMALIES}`}
               title={i18n.ANOMALIES}
+              tooltip={i18n.TOOLTIP}
             />
             <BasicTable items={hosts} columns={columns} pagination={pagination} sorting={sorting} />
           </BasicTableContainer>

x-pack/legacy/plugins/siem/public/components/ml/tables/anomalies_network_table.tsx

@@ -78,6 +78,7 @@ export const AnomaliesNetworkTable = React.memo<AnomaliesNetworkTableProps>(
             <HeaderPanel
               subtitle={`${i18n.SHOWING}: ${networks.length.toLocaleString()} ${i18n.ANOMALIES}`}
               title={i18n.ANOMALIES}
+              tooltip={i18n.TOOLTIP}
             />
             <BasicTable
               items={networks}

x-pack/legacy/plugins/siem/public/components/ml/tables/translations.ts

@@ -14,6 +14,10 @@ export const ANOMALIES = i18n.translate('xpack.siem.anomaliesTable.table.anomali
   defaultMessage: 'Anomalies',
 });
 
+export const TOOLTIP = i18n.translate('xpack.siem.anomaliesTable.table.anomaliesTooltip', {
+  defaultMessage: 'The anomalies table is not filterable via the SIEM global KQL search.',
+});
+
 export const LOADING = i18n.translate('xpack.siem.ml.table.loadingDescription', {
   defaultMessage: 'Loading…',
 });