refactor(dev-infra): use the exec() helper from utils/shelljs whenever possible (#37444)

There is an `exec()` helper provided by `utils/shelljs.ts`, which is a
wrapper around ShellJS' `exec()` with some default options (currently
`silent: true`). The intention is to avoid having to pass these options
to every invocation of the `exec()` function.

This commit updates all code inside `dev-infra/` to use this helper
whenever possible).

NOTE: For simplicity, the `utils/shelljs` helper does not support some
      of the less common call signatures of the original `exec()`
      helper, so in some cases we still need to use the original.

PR Close #37444

dev-infra/release/env-stamp.ts

@@ -6,9 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {exec as _exec} from 'shelljs';
-
-import {info} from '../utils/console';
+import {exec as _exec} from '../utils/shelljs';
 
 /**
  * Log the environment variables expected by bazel for stamping.
@@ -32,7 +30,7 @@ export function buildEnvStamp() {
 
 /** Run the exec command and return the stdout as a trimmed string. */
 function exec(cmd: string) {
-  return _exec(cmd, {silent: true}).toString().trim();
+  return _exec(cmd).trim();
 }
 
 /** Whether the repo has local changes. */