Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements (#18544)

* Performance/Webpack: Introduces more aggressive code-splitting and other perf improvements
- Introduces dynamic imports for built-in plugins
- Uses dynamic imports for various packages (rst2html, brace)
- Introduces route-based dynamic imports
- Splits angular and moment into separate bundles

packages/grafana-data/src/utils/fieldReducer.test.ts

@@ -1,6 +1,7 @@
+import difference from 'lodash/difference';
+
 import { fieldReducers, ReducerID, reduceField } from './fieldReducer';
 
-import _ from 'lodash';
 import { Field, FieldType } from '../types/index';
 import { MutableDataFrame } from './dataFrameHelper';
 import { ArrayVector } from './vector';
@@ -42,7 +43,7 @@ describe('Stats Calculators', () => {
     expect(stats.length).toBe(2);
 
     const found = stats.map(v => v.id);
-    const notFound = _.difference(names, found);
+    const notFound = difference(names, found);
     expect(notFound.length).toBe(2);
 
     expect(notFound[0]).toBe('not a stat');

packages/grafana-data/src/utils/rangeutil.ts

@@ -1,5 +1,5 @@
-// @ts-ignore
-import _ from 'lodash';
+import each from 'lodash/each';
+import groupBy from 'lodash/groupBy';
 
 import { RawTimeRange } from '../types/time';
 
@@ -64,12 +64,12 @@ const rangeOptions = [
 const absoluteFormat = 'YYYY-MM-DD HH:mm:ss';
 
 const rangeIndex: any = {};
-_.each(rangeOptions, (frame: any) => {
+each(rangeOptions, (frame: any) => {
   rangeIndex[frame.from + ' to ' + frame.to] = frame;
 });
 
 export function getRelativeTimesList(timepickerSettings: any, currentDisplay: any) {
-  const groups = _.groupBy(rangeOptions, (option: any) => {
+  const groups = groupBy(rangeOptions, (option: any) => {
     option.active = option.display === currentDisplay;
     return option.section;
   });