refact: remove linux headless (#15866)

* refact: remove linux headless

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(linux): probe DRM availability asynchronously on login

Signed-off-by: fufesou <linlong1266@gmail.com>

* revert changes in drm_capturer.rs

Signed-off-by: fufesou <linlong1266@gmail.com>

* Update submodule hbb_common

Signed-off-by: fufesou <linlong1266@gmail.com>

* docs(linux): clarify DRM availability comments

Remove stale headless and unauthenticated-request
wording, and document the Available-only login-screen gate.

Signed-off-by: fufesou <linlong1266@gmail.com>

* fix(linux): remove unreachable session cleanup branch

Remove the obsolete empty-session path and
clarify the intended use of cached DRM availability.

Signed-off-by: fufesou <linlong1266@gmail.com>

---------

Signed-off-by: fufesou <linlong1266@gmail.com>

flatpak/rustdesk.json

@@ -21,18 +21,6 @@
         }
       ]
     },
-    {
-      "name": "pam",
-      "buildsystem": "autotools",
-      "config-opts": ["--disable-selinux"],
-      "sources": [
-        {
-          "type": "archive",
-          "url": "https://github.com/linux-pam/linux-pam/releases/download/v1.3.1/Linux-PAM-1.3.1.tar.xz",
-          "sha256": "eff47a4ecd833fbf18de9686632a70ee8d0794b79aecb217ebd0ce11db4cd0db"
-        }
-      ]
-    },
     {
       "name": "rustdesk",
       "buildsystem": "simple",
@@ -63,4 +51,4 @@
     "--socket=pulseaudio",
     "--talk-name=org.freedesktop.Flatpak"
   ]
-}
+}