Remove DartPad tutorial best practices (dart-lang#5383)

Support for tests/solutions/hints/etc (at least in their current form)
is going away soon in embedded DartPads, so I don't think we should be
surfacing guidelines on how to best use them.

This PR removes that page and redirects to an underlying paper which
publishes some of the same findings.

Contributes to dart-lang#5382

firebase.json

@@ -228,8 +228,8 @@
       { "source": "/pub/tools/editor", "destination": "/tools", "type": 301 },
       { "source": "/redirects/sdk-download-*", "destination": "/get-dart", "type": 301 },
       { "source": "/resources/dart-tips*{,/**}", "destination": "/effective-dart", "type": 301 },
-      { "source": "/resources/dartpad-best-practices", "destination": "/tools/dartpad/dartpad-best-practices", "type": 301 },
-      { "source": "/resources/dartpad-tutorials.pdf", "destination": "/tools/dartpad/dartpad-best-practices", "type": 301 },
+      { "source": "/resources/dartpad-best-practices", "destination": "https://doi.org/10.1145/3397537.3397558", "type": 301 },
+      { "source": "/resources/dartpad-tutorials.pdf", "destination": "https://doi.org/10.1145/3397537.3397558", "type": 301 },
       { "source": "/samples", "destination": "/language", "type": 301 },
       { "source": "/samples/spirodraw{,/**}", "destination": "/language", "type": 301 },
       { "source": "/samples/todomvc{,/**}", "destination": "/language", "type": 301 },
@@ -261,6 +261,7 @@
       { "source": "/tools/dartfix", "destination": "/tools/dart-fix", "type": 301 },
       { "source": "/tools/dartfmt", "destination": "/tools/dart-format", "type": 301 },
       { "source": "/tools/dartium?(.html)", "destination": "/tools#ides-and-editors", "type": 301 },
+      { "source": "/tools/dartpad/dartpad-best-practices", "destination": "https://doi.org/10.1145/3397537.3397558", "type": 301 },
       { "source": "/tools/debian?(.html)", "destination": "/get-dart", "type": 301 },
       { "source": "/tools/docgen{,/**}", "destination": "/tools/dart-doc", "type": 301 },
       { "source": "/tools/download-archive{,/**}", "destination": "/get-dart/archive", "type": 301 },

src/_data/side-nav.yml

@@ -263,8 +263,6 @@
           - title: Overview
             match-page-url-exactly: true
             permalink: /tools/dartpad
-          - title: DartPad in tutorials
-            permalink: /tools/dartpad/dartpad-best-practices
           - title: Troubleshooting DartPad
             permalink: /tools/dartpad/troubleshoot
   - title: Command-line tools

src/codelabs/async-await.md

@@ -1095,10 +1095,6 @@ are some suggestions for where to go next:
     (Start with [isolates and event loops.][article])
 - [Get the Dart SDK.](/get-dart)
 
-If you're interested in using embedded DartPads, like this codelab does, see
-[best practices for using DartPad in tutorials][].
-
-[best practices for using DartPad in tutorials]: /tools/dartpad/dartpad-best-practices
 [Dart videos]: https://www.youtube.com/playlist?list=PLjxrf2q8roU0Net_g1NT5_vOO3s_FR02J
 [article]: https://medium.com/dartlang/dart-asynchronous-programming-isolates-and-event-loops-bffc3e296a6a
 [Future]: {{site.dart-api}}/{{site.data.pkg-vers.SDK.channel}}/dart-async/Future-class.html

src/resources/index.md

@@ -12,11 +12,6 @@ Check out the following Dart language resources:
     <h3><a href="/resources/books">Books</a></h3>
     <p>A collection of books about Dart.</p>
   </div>
-
-  <div class="card">
-    <h3><a href="/resources/dartpad-best-practices">DartPad in tutorials: Best practices</a></h3>
-    <p>A guide to using embedded DartPads in educational content for Dart and Flutter users.</p>
-  </div>
 
   <div class="card">
     <h3><a href="/code-of-conduct">Code of conduct</a></h3>