Move bbappends into a bbappend subdirectory

They are now sorted depending on which layer the origin bb recipe is
located.

BugzID: 74466

conf/layer.conf

@@ -3,7 +3,9 @@ BBPATH .= ":${LAYERDIR}"
 
 # We have recipes-* directories, add to BBFILES
 BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
-	    ${LAYERDIR}/recipes-*/*/*.bbappend"
+            ${LAYERDIR}/recipes-*/*/*.bbappend \
+            ${LAYERDIR}/bbappends/*/recipes-*/*/*.bbappend \
+        "
 
 BBFILE_COLLECTIONS += "netmodule-distro"
 BBFILE_PATTERN_netmodule-distro = "^${LAYERDIR}/"