Configurable bus name

[yofukashino]

According to this,

ComposeNativeTray/src/native/linux/sni.c

Line 158 in 2e093a5

char *bus_name; /* org.kde.StatusNotifierItem-{PID}-1 */

The bus name will always be org.kde.StatusNotifierItem-{PID}-1 and if some other app already has that it just fails silently. (Happens with flatpak apps since it doesnt reveal all the proc)

Maybe make it configureable to use a custom string from env variables? Something like ComposeNativeTrayBusId and if that isn't set then fallback to PID.

Or do something like done with with mpris, org.mpris.MediaPlayer2.{name} and subsequent are registered under it as org.mpris.MediaPlayer2.{name}.*, perhaps org.kde.StatusNotifierItem.{name}.

Also, switch to using org.freedesktop.StatusNotifierItem as that is the standard.