bpo-41028: Doc: Move switchers to docsbuild-scripts. (GH-20969)

diff --git a/Doc/tools/templates/dummy.html b/Doc/tools/templates/dummy.html
index 68ae3ad..3438b44 100644
--- a/Doc/tools/templates/dummy.html
+++ b/Doc/tools/templates/dummy.html
@@ -6,3 +6,12 @@
 {% trans %}CPython implementation detail:{% endtrans %}
 {% trans %}Deprecated since version {deprecated}, will be removed in version {removed}{% endtrans %}
 {% trans %}Deprecated since version {deprecated}, removed in version {removed}{% endtrans %}
+
+
+In docsbuild-scripts, when rewriting indexsidebar.html with actual versions:
+
+{% trans %}in development{% endtrans %}
+{% trans %}pre-release{% endtrans %}
+{% trans %}stable{% endtrans %}
+{% trans %}security-fixes{% endtrans %}
+{% trans %}EOL{% endtrans %}
diff --git a/Doc/tools/templates/indexsidebar.html b/Doc/tools/templates/indexsidebar.html
index 1c1cb54..f7bf6d8 100644
--- a/Doc/tools/templates/indexsidebar.html
+++ b/Doc/tools/templates/indexsidebar.html
@@ -2,12 +2,8 @@
 <p><a href="{{ pathto('download') }}">{% trans %}Download these documents{% endtrans %}</a></p>
 <h3>{% trans %}Docs by version{% endtrans %}</h3>
 <ul>
-  <li><a href="https://docs.python.org/3.10/">{% trans %}Python 3.10 (in development){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.9/">{% trans %}Python 3.9 (pre-release){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.8/">{% trans %}Python 3.8 (stable){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.7/">{% trans %}Python 3.7 (stable){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/3.6/">{% trans %}Python 3.6 (security-fixes){% endtrans %}</a></li>
-  <li><a href="https://docs.python.org/2.7/">{% trans %}Python 2.7 (EOL){% endtrans %}</a></li>
+  <li><a href="https://docs.python.org/">{% trans %}Stable{% endtrans %}</a></li>
+  <li><a href="https://docs.python.org/dev/">{% trans %}In development{% endtrans %}</a></li>
   <li><a href="https://www.python.org/doc/versions/">{% trans %}All versions{% endtrans %}</a></li>
 </ul>
 
diff --git a/Doc/tools/templates/layout.html b/Doc/tools/templates/layout.html
index 17592d7..98ccf42 100644
--- a/Doc/tools/templates/layout.html
+++ b/Doc/tools/templates/layout.html
@@ -12,22 +12,14 @@
 
 {% block rootrellink %}
 {{ super() }}
-    <li>
-      {%- if switchers is defined %}
-      <span class="language_switcher_placeholder">{{ language or 'en' }}</span>
-      <span class="version_switcher_placeholder">{{ release }}</span>
-      <a href="{{ pathto('index') }}">{% trans %}Documentation {% endtrans %}</a>{{ reldelim1 }}
-      {%- else %}
+    <li id="cpython-language-and-version">
       <a href="{{ pathto('index') }}">{{ shorttitle }}</a>{{ reldelim1 }}
-      {%- endif %}
     </li>
 {% endblock %}
 
 {% block extrahead %}
     <link rel="canonical" href="https://docs.python.org/3/{{pagename}}.html" />
     {% if builder != "htmlhelp" %}
-      {% if switchers is defined and not embedded %}
-      <script type="text/javascript" src="{{ pathto('_static/switchers.js', 1) }}"></script>{% endif %}
       {% if pagename == 'whatsnew/changelog' and not embedded %}
       <script type="text/javascript" src="{{ pathto('_static/changelog_search.js', 1) }}"></script>{% endif %}
     {% endif %}