docs: Move all ports docs to the single ToC.

Previously, only "selected chapters" were shown in left-pane ToC (of
Read The Docs theme). These chapters were selected out of order. The
rest of chapters were hidden beyond "Documentation Contents" pseudo-
chapter. This arguably led only to confusion, as many people probably
never tried to open that pseudo-chapter, and those who did, were
confused. Such organization is even worse for PDF output, causing
chapters go in mix-mashed order.

So, instead move to single clean ToC. This will allow readers of HTML
to have access to any doc content at their fingertips (and straight
before their eyes), and will allow to finally have clean PDF docs.

docs/esp8266_contents.rst

-MicroPython documentation contents
-==================================
-
-.. toctree::
-
-    esp8266/quickref.rst
-    esp8266/general.rst
-    esp8266/tutorial/index.rst
-    library/index.rst
-    reference/index.rst
-    genrst/index.rst
-    license.rst

docs/esp8266_index.rst

@@ -4,10 +4,12 @@ MicroPython documentation and references
 .. toctree::
 
     esp8266/quickref.rst
+    esp8266/general.rst
+    esp8266/tutorial/index.rst
     library/index.rst
+    reference/index.rst
     genrst/index.rst
     license.rst
-    esp8266_contents.rst
 
 Indices and tables
 ==================

docs/pyboard_contents.rst

-MicroPython documentation contents
-==================================
-
-.. toctree::
-
-    pyboard/quickref.rst
-    pyboard/general.rst
-    pyboard/tutorial/index.rst
-    library/index.rst
-    reference/index.rst
-    pyboard/hardware/index.rst
-    genrst/index.rst
-    license.rst
-

docs/pyboard_index.rst

@@ -6,11 +6,11 @@ MicroPython documentation and references
     pyboard/quickref.rst
     pyboard/general.rst
     pyboard/tutorial/index.rst
-    library/index.rst
     pyboard/hardware/index.rst
+    library/index.rst
+    reference/index.rst
     genrst/index.rst
     license.rst
-    pyboard_contents.rst
 
 Indices and tables
 ==================

docs/topindex.html

@@ -88,7 +88,7 @@
     </td>
     <td width="40%" style="padding-left:2em;">
       <p class="biglink">
-        <a class="biglink" href="{{ pathto(port + "_contents") }}">Table of contents</a><br/>
+        <a class="biglink" href="{{ pathto(port + "_index") }}">Table of contents</a><br/>
         <span class="linkdescr">a list of all sections and subsections</span>
       </p>
     </td></tr>

docs/unix_contents.rst

-MicroPython documentation contents
-==================================
-
-.. toctree::
-
-    library/index.rst
-    reference/index.rst
-    genrst/index.rst
-    license.rst

docs/unix_index.rst

@@ -4,9 +4,9 @@ MicroPython documentation and references
 .. toctree::
 
     library/index.rst
+    reference/index.rst
     genrst/index.rst
     license.rst
-    unix_contents.rst
 
 Indices and tables
 ==================

docs/wipy_contents.rst

-MicroPython documentation contents
-==================================
-
-.. toctree::
-
-    wipy/quickref.rst
-    wipy/general.rst
-    wipy/tutorial/index.rst
-    library/index.rst
-    reference/index.rst
-    genrst/index.rst
-    license.rst

docs/wipy_index.rst

@@ -7,9 +7,9 @@ MicroPython documentation and references
     wipy/general.rst
     wipy/tutorial/index.rst
     library/index.rst
+    reference/index.rst
     genrst/index.rst
     license.rst
-    wipy_contents.rst
 
 Indices and tables
 ==================