fix(ngcc): do not use cached file-system (#36687)

The cached file-system was implemented to speed up ngcc
processing, but in reality most files are not accessed many times
and there is no noticeable degradation in speed by removing it.

Benchmarking `ngcc -l debug` for AIO on a local machine
gave a range of 196-236 seconds with the cache and 197-224
seconds without the cache.

Moreover, when running in parallel mode, ngcc has a separate
file cache for each process. This results in excess memory usage.
Notably the master process, which only does analysis of entry-points
holds on to up to 500Mb for AIO when using the cache compared to
only around 30Mb when not using the cache.

Finally, the file-system cache being incorrectly primed with file
contents before being processed has been the cause of a number
of bugs. For example https://github.com/angular/angular-cli/issues/16860#issuecomment-614694269.

PR Close #36687

packages/compiler-cli/ngcc/main-ngcc.ts

@@ -6,7 +6,6 @@
  * 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 {setFileSystem, CachedFileSystem, NodeJSFileSystem} from '../src/ngtsc/file_system';
 import {mainNgcc} from './src/main';
 import {parseCommandLineOptions} from './src/command_line_options';
 
@@ -14,7 +13,6 @@ import {parseCommandLineOptions} from './src/command_line_options';
 if (require.main === module) {
   process.title = 'ngcc';
   const startTime = Date.now();
-  setFileSystem(new CachedFileSystem(new NodeJSFileSystem()));
   const options = parseCommandLineOptions(process.argv.slice(2));
   (async () => {
     try {