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/src/execution/cluster/worker.ts

@@ -9,7 +9,6 @@
 
 import * as cluster from 'cluster';
 
-import {CachedFileSystem, NodeJSFileSystem, setFileSystem} from '../../../../src/ngtsc/file_system';
 import {parseCommandLineOptions} from '../../command_line_options';
 import {ConsoleLogger} from '../../logging/console_logger';
 import {Logger, LogLevel} from '../../logging/logger';
@@ -28,8 +27,6 @@ if (require.main === module) {
     process.title = 'ngcc (worker)';
 
     try {
-      setFileSystem(new CachedFileSystem(new NodeJSFileSystem()));
-
       const {
         createNewEntryPointFormats = false,
         logger = new ConsoleLogger(LogLevel.info),