Autofill service fallback FF (#5836)

Task/Issue URL:
https://app.asana.com/0/1149059203486286/1209843796003365/f

### Description
See: https://app.asana.com/0/488551667048375/1209843796003365/f

TLDR; adds an extra fallback FF in case we can't rely on the parent FF

### Steps to test this PR

N/A

### UI changes
| Before  | After |
| ------ | ----- |
!(Upload before screenshot)|(Upload after screenshot)|

Author: cmonfortep

autofill/autofill-impl/src/main/java/com/duckduckgo/autofill/impl/service/AutofillServiceFeature.kt

@@ -44,4 +44,7 @@ interface AutofillServiceFeature {
     @Toggle.DefaultValue(false)
     @InternalAlwaysEnabled
     fun canAutofillInsideDDG(): Toggle
+
+    @Toggle.DefaultValue(true)
+    fun canProcessSystemFillRequests(): Toggle
 }

autofill/autofill-impl/src/main/java/com/duckduckgo/autofill/impl/service/RealAutofillService.kt

@@ -76,7 +76,7 @@ class RealAutofillService : AutofillService() {
 
         autofillJob += coroutineScope.launch(dispatcherProvider.io()) {
             runCatching {
-                if (autofillServiceFeature.self().isEnabled().not()) {
+                if (isAutofillServiceEnabled().not()) {
                     callback.onSuccess(null)
                     return@launch
                 }
@@ -169,6 +169,10 @@ class RealAutofillService : AutofillService() {
         Timber.v("DDGAutofillService onDisconnected")
     }
 
+    private fun isAutofillServiceEnabled(): Boolean {
+        return autofillServiceFeature.self().isEnabled() && autofillServiceFeature.canProcessSystemFillRequests().isEnabled()
+    }
+
     companion object {
         private val DDG_PACKAGE_IDS = setOf(
             "com.duckduckgo.mobile.android",