Revert "Reorganize and clarify API doc generator" (#132613)

Reverts flutter/flutter#132353

Educated guess that this is causing the docs failures: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8772644466113801713/+/u/Docs/Deploy_docs/Firebase_deploy/stdout

dev/docs/dashing_postprocess.dart

@@ -0,0 +1,29 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:io';
+
+/// This changes the DocSetPlatformFamily key to be "dartlang" instead of the
+/// name of the package (usually "flutter").
+///
+/// This is so that the IntelliJ plugin for Dash will be able to go directly to
+/// the docs for a symbol from a keystroke. Without this, flutter isn't part
+/// of the list of package names it searches. After this, it finds the flutter
+/// docs because they're declared here to be part of the "dartlang" family of
+/// docs.
+///
+/// Dashing doesn't have a way to configure this, so we modify the Info.plist
+/// directly to make the change.
+void main(List<String> args) {
+  final File infoPlist = File('flutter.docset/Contents/Info.plist');
+  String contents = infoPlist.readAsStringSync();
+
+  // Since I didn't want to add the XML package as a dependency just for this,
+  // I just used a regular expression to make this simple change.
+  final RegExp findRe = RegExp(r'(\s*<key>DocSetPlatformFamily</key>\s*<string>)[^<]+(</string>)', multiLine: true);
+  contents = contents.replaceAllMapped(findRe, (Match match) {
+    return '${match.group(1)}dartlang${match.group(2)}';
+  });
+  infoPlist.writeAsStringSync(contents);
+}