Datasource: updates PromExploreQueryEditor to prevent it from throwing error on edit (#21605)

* Datasource: updates PromExploreQueryEditor - rewrite to functional component

* Datasource: updates PromQueryField - moves an extra field from children to the separate prop

* Datasource: adds PromExploreExtraField

* Datasource: updates PromExploreQueryEditor - fixes typo

* Datasource: updates prometheus explore editor snapshots

* Datasource: updates PromExploreExtraField export

* Datasource: removes unnecessary div from PromExploreQueryEditor

* Datasource: adds basic PromExploreExtraField snapshot test

* Datasource: adds basic PromExploreQueryEditor test

* Datasource: updates PromExploreQueryEditor snapshot to fix timezone issues

* Datasource: updates PromExploreQueryEditor - onChangeQueryStep cleanup

* Datasource: updates PromExploreQueryEditor test to check ExtraFieldElement render

* Datasource: simplified PromExploreQueryEditor onStepChange method

* Datasource: updates Prometheus module import

* Datasource: updates PromExploreQueryEditor test

* Datasource: updates PromExploreQueryEditor tests

* Datasource: fixes PromExploreQueryEditor error on empty interval init

* Datasource: adds a tooltip to PromExploreExtraField mounted in PromExploreQueryEditor

* Datasource: updates PromExploreQueryEditor snapshots

public/app/plugins/datasource/prometheus/components/PromExploreExtraField.test.tsx

@@ -0,0 +1,28 @@
+import React from 'react';
+import { shallow } from 'enzyme';
+import { PromExploreExtraField, PromExploreExtraFieldProps } from './PromExploreExtraField';
+
+const setup = (propOverrides?: PromExploreExtraFieldProps) => {
+  const label = 'Prometheus Explore Extra Field';
+  const value = '123';
+  const onChangeFunc = jest.fn();
+  const onKeyDownFunc = jest.fn();
+
+  const props: any = {
+    label,
+    value,
+    onChangeFunc,
+    onKeyDownFunc,
+  };
+
+  Object.assign(props, propOverrides);
+
+  return shallow(<PromExploreExtraField {...props} />);
+};
+
+describe('PrometheusExploreExtraField', () => {
+  it('should render component', () => {
+    const wrapper = setup();
+    expect(wrapper).toMatchSnapshot();
+  });
+});