[ML] Data Frames - Creation wizard editor for source config (elastic#…

…41937) (elastic#42171)

* Advanced editor for source config

* Separate editor for source and pivot

* Reset query when toggle back to KQL if changes have been made. Show warning

* update snapshot

* retain source config editor state. display in code block

* ensure apply button set correctly

* update source config editor helptext

* update request and step_define_summary test

* update step_define_summary snapshot

* No source editor switch if saved search.

x-pack/legacy/plugins/ml/public/data_frame/common/request.test.ts

@@ -133,7 +133,9 @@ describe('Data Frame: Common', () => {
     const pivotState: StepDefineExposedState = {
       aggList: { 'the-agg-name': agg },
       groupByList: { 'the-group-by-name': groupBy },
-      isAdvancedEditorEnabled: false,
+      isAdvancedPivotEditorEnabled: false,
+      isAdvancedSourceEditorEnabled: false,
+      sourceConfigUpdated: false,
       searchString: 'the-query',
       searchQuery: 'the-search-query',
       valid: true,