Revert Dual Web Compile changes (#143175)

Dual Web Compile has had some issues where `flutter test` is not respecting the `--web-renderer` flag for some reason. I haven't gotten entirely to the bottom of the issue, but for now we need to rever these changes while I investigate. This reverts the following PRs:

https://github.com/flutter/flutter/pull/143128
https://github.com/flutter/flutter/pull/141396

While doing this revert, I had a few merge conflicts with https://github.com/flutter/flutter/pull/142760, and I tried to resolve the merge conflicts within the spirit of that PR's change, but @chingjun I might need your input on whether the imports I have modified are okay with regards to the change you were making.

dev/devicelab/lib/tasks/web_benchmarks.dart

@@ -39,7 +39,7 @@ Future<TaskResult> runWebBenchmark(WebBenchmarkOptions benchmarkOptions) async {
         '--omit-type-checks',
       ],
       '--dart-define=FLUTTER_WEB_ENABLE_PROFILING=true',
-      if (!benchmarkOptions.useWasm) '--web-renderer=${benchmarkOptions.webRenderer}',
+      '--web-renderer=${benchmarkOptions.webRenderer}',
       '--profile',
       '--no-web-resources-cdn',
       '-t',
@@ -125,7 +125,7 @@ Future<TaskResult> runWebBenchmark(WebBenchmarkOptions benchmarkOptions) async {
         return Response.internalServerError(body: '$error');
       }
     }).add(createBuildDirectoryHandler(
-      path.join(macrobenchmarksDirectory, 'build', 'web'),
+      path.join(macrobenchmarksDirectory, 'build', benchmarkOptions.useWasm ? 'web_wasm' : 'web'),
     ));
 
     server = await io.HttpServer.bind('localhost', benchmarkServerPort);