No class loading if Java features disabled

- No longer loads custom classes if not needed for respective packages
- Renames isGmsUnstable to isDroidGuardOrVending
- Removes spoofVendingSdk from migrate/autopif scripts (don't document yet)
- Adds missing setAccessible() call for early return in EntryPointVending.init()
- Adds missing set of spoofSignature -> 0 for vending

app/src/main/java/es/chiteroman/playintegrityfix/EntryPointVending.java

@@ -23,6 +23,7 @@ public final class EntryPointVending {
             oldValue = field.getInt(null);
             if (oldValue == targetSdk) {
                 if (verboseLogs > 2) LOG(String.format("[SDK_INT]: %d (unchanged)", oldValue));
+                field.setAccessible(false);
                 return;
             }
             field.set(null, targetSdk);