iPhone Duo: limit from Apple's reference data instead of a cut to 10, --duo-only; shared asset library helpers in their own module

cli/data/flags.json

@@ -106,7 +106,7 @@
    "name"
   ],
   "apple cpp": [
-   "add-for-review",
+   "duo-only",
    "include-drafts",
    "jobs",
    "name",
@@ -117,7 +117,6 @@
    "repair-stuck",
    "src",
    "variant",
-   "verify",
    "write"
   ],
   "apple creative-assets": [
@@ -206,7 +205,7 @@
    "write"
   ],
   "apple ppo": [
-   "add-for-review",
+   "duo-only",
    "experiment",
    "include-drafts",
    "jobs",
@@ -218,7 +217,6 @@
    "src",
    "traffic",
    "variant",
-   "verify",
    "write"
   ],
   "apple preorder": [
@@ -274,7 +272,7 @@
    "platform"
   ],
   "apple screenshots": [
-   "add-for-review",
+   "duo-only",
    "include-drafts",
    "jobs",
    "not-sent-for-review",
@@ -283,7 +281,6 @@
    "repair-stuck",
    "src",
    "variant",
-   "verify",
    "write"
   ],
   "apple signing": [
@@ -1119,6 +1116,7 @@
    "cordova-android",
    "cordova-ios",
    "days",
+   "duo-only",
    "expo",
    "flutter",
    "godot",
@@ -1250,6 +1248,7 @@
    "device",
    "dir",
    "download",
+   "duo-only",
    "enable",
    "end",
    "entitlements",
@@ -1594,7 +1593,7 @@
    "storebound apple review-details [--platform ios|macos|tvos|visionos] [--contact-from <Apple ID of another app>] [--dry]"
   ],
   "apple screenshots": [
-   "storebound apple screenshots [--src store/renders] [--only en-US,tr] [--jobs 4] [--variant b] [--dry]",
+   "storebound apple screenshots [--src store/renders] [--only en-US,tr] [--jobs 4] [--variant b] [--duo-only] [--dry]",
    "storebound apple screenshots --repair-stuck [--dry]   (only the screenshots stuck outside COMPLETE, in place)"
   ],
   "apple signing": [