Core: Adding DashboardPicker component (#18811)

* Adding DashboardPicker component

* fix prop names

* fix prop names pt2

public/app/core/components/Select/DashboardPicker.tsx

+import React, { PureComponent } from 'react';
+import { AsyncSelect } from '@grafana/ui';
+import { debounce } from 'lodash';
+import { getBackendSrv } from 'app/core/services/backend_srv';
+import { DashboardSearchHit, DashboardDTO } from 'app/types';
+
+export interface Props {
+  className?: string;
+  onSelected: (dashboard: DashboardDTO) => void;
+}
+
+export interface State {
+  isLoading: boolean;
+}
+
+export class DashboardPicker extends PureComponent<Props, State> {
+  debouncedSearch: any;
+
+  constructor(props: Props) {
+    super(props);
+
+    this.state = {
+      isLoading: false,
+    };
+
+    this.debouncedSearch = debounce(this.getDashboards, 300, {
+      leading: true,
+      trailing: true,
+    });
+  }
+
+  getDashboards = (query = '') => {
+    this.setState({ isLoading: true });
+    return getBackendSrv()
+      .search({ type: 'dash-db', query })
+      .then((result: DashboardSearchHit[]) => {
+        const dashboards = result.map((item: DashboardSearchHit) => {
+          return {
+            id: item.uid,
+            value: item.id,
+            label: `${item.folderTitle ? item.folderTitle : 'General'}/${item.title}`,
+          };
+        });
+
+        this.setState({ isLoading: false });
+        return dashboards;
+      });
+  };
+
+  render() {
+    const { className, onSelected } = this.props;
+    const { isLoading } = this.state;
+
+    return (
+      <div className="gf-form-inline">
+        <div className="gf-form">
+          <AsyncSelect
+            className={className}
+            isLoading={isLoading}
+            isClearable={true}
+            defaultOptions={true}
+            loadOptions={this.debouncedSearch}
+            onChange={onSelected}
+            placeholder="Select dashboard"
+            noOptionsMessage={() => 'No dashboards found'}
+          />
+        </div>
+      </div>
+    );
+  }
+}