pythonDocs: 3.7 -> 3.10

Also include texinfo docs for Python 3 (they aren't generated for
Python 2)

A few minor fixes had to be made to generate.sh as well.

pkgs/development/interpreters/python/cpython/docs/3.10-html.nix

@@ -0,0 +1,18 @@
+# This file was generated and will be overwritten by ./generate.sh
+
+{ stdenv, fetchurl, lib }:
+
+stdenv.mkDerivation {
+  name = "python310-docs-html-3.10.7";
+  src = fetchurl {
+    url = http://www.python.org/ftp/python/doc/3.10.7/python-3.10.7-docs-html.tar.bz2;
+    sha256 = "0j86z1vmaghzj5i4frvzyfb9qwsmm09g4f4ssx5w27cm30b8k0v1";
+  };
+  installPhase = ''
+    mkdir -p $out/share/doc/python310
+    cp -R ./ $out/share/doc/python310/html
+  '';
+  meta = {
+    maintainers = [ ];
+  };
+}