feat: introduce source maps for templates (#15011)

The main use case for the generated source maps is to give
errors a meaningful context in terms of the original source
that the user wrote.

Related changes that are included in this commit:

* renamed virtual folders used for jit:
  * ng://<module type>/module.ngfactory.js
  * ng://<module type>/<comp type>.ngfactory.js
  * ng://<module type>/<comp type>.html (for inline templates)
* error logging:
  * all errors that happen in templates are logged
    from the place of the nearest element.
  * instead of logging error messages and stacks separately,
    we log the actual error. This is needed so that browsers apply
    source maps to the stack correctly.
  * error type and error is logged as one log entry.

Note that long-stack-trace zone has a bug that 
disables source maps for stack traces,
see https://github.com/angular/zone.js/issues/661.

BREAKING CHANGE:

- DebugNode.source no more returns the source location of a node.  

Closes 14013

packages/compiler/test/output/source_map_util.ts

@@ -0,0 +1,38 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {SourceMap} from '@angular/compiler/src/output/source_map';
+const b64 = require('base64-js');
+const SourceMapConsumer = require('source-map').SourceMapConsumer;
+
+export interface SourceLocation {
+  line: number;
+  column: number;
+  source: string;
+}
+
+export function originalPositionFor(
+    sourceMap: SourceMap, genPosition: {line: number, column: number}): SourceLocation {
+  const smc = new SourceMapConsumer(sourceMap);
+  // Note: We don't return the original object as it also contains a `name` property
+  // which is always null and we don't want to include that in our assertions...
+  const {line, column, source} = smc.originalPositionFor(genPosition);
+  return {line, column, source};
+}
+
+export function extractSourceMap(source: string): SourceMap {
+  let idx = source.lastIndexOf('\n//#');
+  if (idx == -1) return null;
+  const smComment = source.slice(idx).trim();
+  const smB64 = smComment.split('sourceMappingURL=data:application/json;base64,')[1];
+  return smB64 ? JSON.parse(decodeB64String(smB64)) : null;
+}
+
+function decodeB64String(s: string): string {
+  return b64.toByteArray(s).reduce((s: string, c: number) => s + String.fromCharCode(c), '');
+}