refactor(compiler): remove all source-level traces to tsc-wrapped (#18966)

- temporarily keeps the old sources under packages/tsc-wrapped
  until the build scripts are changed to use compiler-cli everywhere.
- removes the compiler options `disableTransformerPipeline` that was introduced
  in a previous beta of Angular 5, i.e. the transformer based compiler
  is now always enabled.

PR Close #18966

packages/compiler/test/aot/compiler_spec.ts

@@ -7,8 +7,9 @@
  */
 
 import {AotSummaryResolver, GeneratedFile, StaticSymbolCache, StaticSymbolResolver, toTypeScript} from '@angular/compiler';
+import {MetadataBundler} from '@angular/compiler-cli/src/metadata/bundler';
+import {privateEntriesToIndex} from '@angular/compiler-cli/src/metadata/index_writer';
 import {NodeFlags} from '@angular/core/src/view/index';
-import {MetadataBundler, privateEntriesToIndex} from '@angular/tsc-wrapped';
 import * as ts from 'typescript';
 
 import {extractSourceMap, originalPositionFor} from '../output/source_map_util';