Bring back USNF's scripts-only mode for older Android, but better

- do scripts-only mode automatically on Android < 8.0 since it doesn't support Zygisk and generally doesn't need a PIF module to pass at all
- clean up all unused files in scripts-only mode, and modify script behaviors for it, including allowing GMS on DenyList, and even add it if missing since it's necessary on some scripts-only configurations
- allow manually entering scripts-only mode by deleting the zygisk directory of the currently installed module and reinstalling
- intentionally don't alter the Enforce DenyList state, since we don't know what other modules are installed that might depend on it one way or the other, so leave that up to the user

module/customize.sh

@@ -1,10 +1,14 @@
-# Error on < Android 8
-if [ "$API" -lt 26 ]; then
-    abort "! You can't use this module on Android < 8.0"
+# Allow a scripts-only mode on older Android without Zygisk
+if [ "$API" -lt 26 -o ! -d /data/adb/modules/playintegrityfix/zygisk ]; then
+    ui_print "! Installing global scripts only for Android < 8.0; no Zygisk device spoofing possible"
+    rm -rf $MODPATH/classes.dex $MODPATH/common_setup.sh $MODPATH/custom.pif.json \
+        $MODPATH/example.app_replace.list $MODPATH/example.pif.json $MODPATH/migrate.sh $MODPATH/zygisk \
+        /data/adb/modules/playintegrityfix/custom.app_replace.list \
+        /data/adb/modules/playintegrityfix/custom.pif.json /data/adb/modules/playintegrityfix/system
 fi
 
 # Copy any disabled app files to updated module
-if [ -d "/data/adb/modules/playintegrityfix/system" ]; then
+if [ -d /data/adb/modules/playintegrityfix/system ]; then
     ui_print "- Restoring disabled ROM apps configuration"
     cp -arf /data/adb/modules/playintegrityfix/system $MODPATH
 fi
@@ -23,7 +27,7 @@ if [ -d /data/adb/modules/MagiskHidePropsConf ]; then
 fi
 
 # Run common tasks for installation and boot-time
-. $MODPATH/common_setup.sh
+[ -d "$MODPATH/zygisk" ] && . $MODPATH/common_setup.sh
 
 # Migrate custom.pif.json to latest defaults if needed
 if [ -f "$MODPATH/custom.pif.json" ] && ! grep -q "api_level" $MODPATH/custom.pif.json; then