fix(@angular-devkit/build-angular): do not add internal CSS resources files in watch

This change fixes an issue which caused internal virtual inputs to be added to the watch, this cases watchpack to emit a removed event as this file does not exist on disk.

We fix this issue, by prefixing `css-resouces` namespace with `angular:` which the input to be filtered out, see: https://github.com/angular/angular-cli/blob/4539961968e90c8c40ed683afe1cf491630a0048/packages/angular_devkit/build_angular/src/tools/esbuild/bundler-context.ts#L251

Closes #26918

Author: alan-agius4

packages/angular_devkit/build_angular/src/tools/esbuild/stylesheets/css-resource-plugin.ts

@@ -11,6 +11,8 @@ import { readFile } from 'node:fs/promises';
 import { extname, join, relative } from 'node:path';
 import { LoadResultCache, createCachedLoad } from '../load-result-cache';
 
+const CSS_RESOURCE_NAMESPACE = 'angular:css-resource';
+
 /**
  * Symbol marker used to indicate CSS resource resolution is being attempted.
  * This is used to prevent an infinite loop within the plugin's resolve hook.
@@ -97,12 +99,12 @@ export function createCssResourcePlugin(cache?: LoadResultCache): Plugin {
           // Use a relative path to prevent fully resolved paths in the metafile (JSON stats file).
           // This is only necessary for custom namespaces. esbuild will handle the file namespace.
           path: relative(build.initialOptions.absWorkingDir ?? '', result.path),
-          namespace: 'css-resource',
+          namespace: CSS_RESOURCE_NAMESPACE,
         };
       });
 
       build.onLoad(
-        { filter: /./, namespace: 'css-resource' },
+        { filter: /./, namespace: CSS_RESOURCE_NAMESPACE },
         createCachedLoad(cache, async (args) => {
           const resourcePath = join(build.initialOptions.absWorkingDir ?? '', args.path);