Remove debug-tweaks references

We no longer provide this feature, so remove documentation for it. In
most cases, we can replace occurrences of "debug-tweaks" by
"allow-empty-password empty-root-password allow-root-login
post-install-logging" to achieve what this feature previously enabled.

Subtle, but the default local.conf does not include
post-install-logging, so in parts where there is mention of the default
local.conf file, adjust the documentation to only mention the first
three above.

In the intro manual, instead of providing instructions that replace
EXTRA_IMAGE_FEATURES entirely, provide ones that append
EXTRA_IMAGE_FEATURES.

(From yocto-docs rev: f0efd4c7df91863304b92514664bdd1fa62b1fbb)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/features.rst

@@ -285,31 +285,24 @@ The image features available for all images are:
 -  *dbg-pkgs:* Installs debug symbol packages for all packages installed
    in a given image.
 
--  *debug-tweaks:* Makes an image suitable for development (e.g. allows
-   root logins, logins without passwords ---including root ones, and enables
-   post-installation logging). See the ``allow-empty-password``,
-   ``allow-root-login``, ``empty-root-password``, and ``post-install-logging``
-   features in this list for additional information.
-
 -  *dev-pkgs:* Installs development packages (headers and extra library
    links) for all packages installed in a given image.
 
 -  *doc-pkgs:* Installs documentation packages for all packages
    installed in a given image.
 
--  *empty-root-password:* This feature or ``debug-tweaks`` is required if
-   you want to allow root login with an empty password. If these features
-   are not present in :term:`IMAGE_FEATURES`, a non-empty password is
-   forced in ``/etc/passwd`` and ``/etc/shadow`` if such files exist.
+-  *empty-root-password:* This feature can be used if you want to allow root
+   login with an empty password. If this feature is not present in
+   :term:`IMAGE_FEATURES`, a non-empty password is forced in ``/etc/passwd`` and
+   ``/etc/shadow`` if such files exist.
 
    .. note::
        ``empty-root-password`` doesn't set an empty root password by itself.
        You get an initial empty root password thanks to the
        :oe_git:`base-passwd </openembedded-core/tree/meta/recipes-core/base-passwd/>`
        and :oe_git:`shadow </openembedded-core/tree/meta/recipes-extended/shadow/>`
-       recipes, and the presence of ``empty-root-password`` or ``debug-tweaks``
-       just disables the mechanism which forces an non-empty password for the
-       root user.
+       recipes, and the presence of ``empty-root-password`` just disables the
+       mechanism which forces an non-empty password for the root user.
 
 -  *lic-pkgs:* Installs license packages for all packages installed in a
    given image.

documentation/ref-manual/variables.rst

@@ -2604,10 +2604,14 @@ system and gives an overview of their function and contents.
         - "dbg-pkgs" --- adds -dbg packages for all installed packages including
           symbol information for debugging and profiling.
 
-        - "debug-tweaks" --- makes an image suitable for debugging. For example, allows root logins without passwords and
-          enables post-installation logging. See the 'allow-empty-password' and
-          'post-install-logging' features in the ":ref:`ref-features-image`"
-          section for more information.
+        - "empty-root-password" --- This feature can be used if you want to
+          allow root login with an empty password.
+        - "allow-empty-password" --- Allows Dropbear and OpenSSH to accept
+          logins from accounts having an empty password string.
+        - "allow-root-login" --- Allows Dropbear and OpenSSH to accept root logins.
+        - "post-install-logging" --- Enables logging postinstall script runs to
+          the ``/var/log/postinstall.log`` file on first boot of the image on
+          the target system.
         - "dev-pkgs" --- adds -dev packages for all installed packages. This is
           useful if you want to develop against the libraries in the image.
         - "read-only-rootfs" --- creates an image whose root filesystem is