Add component: Cascader (#21410)

* Rename old cascader

* Change name of old cascader

* Add basic cascader without search

* Add basic cascader without search

* Flatten options to make it searchable

* Add regex search and make backspace work

* Add barebone search without styles

* Add SearchResult list

* Add search navigation

* Rewrite of cascader and add some things to SelectBase

* Make SelectBase controlllable

* Cleanup

* Add initial value functionality

* Add onblur to hand caret direction

* New storyboom format for ButtonCascader

* Add knobs to story

* Add story and docs for UnitPicker

* Make UnitPicker use Cascader

* Fix backspace issue and empty value

* Fix backspace issue for real

* Remove unused code

* Fix focus issue

* Change children to items and remove ButtonCascaderProps

* Remove local CascaderOption

* Fix failed test

* Revert UnitPicker changes and change format for ButtonCascader

* Fix failing tests

public/app/plugins/datasource/loki/components/LokiQueryFieldForm.tsx

@@ -2,7 +2,7 @@
 import React from 'react';
 
 import {
-  Cascader,
+  ButtonCascader,
   CascaderOption,
   SlatePrism,
   TypeaheadOutput,
@@ -148,7 +148,7 @@ export class LokiQueryFieldForm extends React.PureComponent<LokiQueryFieldFormPr
       <>
         <div className="gf-form-inline">
           <div className="gf-form">
-            <Cascader
+            <ButtonCascader
               options={logLabelOptions || []}
               disabled={buttonDisabled}
               buttonText={chooserText}