Keep playlist affordances where an empty list took them

Three things live testing found, all of them where a playlist list or a
playlist is empty.

The picker said "This playlist has no videos" when there were no
playlists to pick — copy about a playlist's contents standing in for
copy about the list of them. Each section now says it has none, scoped
to where it is: the device, or that account. An account whose fetch came
back empty said nothing at all and left a bare gap.

The browse view's Playlists tab fetched into its own state, so a
playlist created through the picker — which goes through the shared
cache — never appeared, and nothing refetched on coming back to the tab.
It reads the cache now, and selecting the tab always refetches with the
rows already there kept on screen. The cache is keyed by account, which
is the discard on an account change the private copy needed a generation
for.

Removing the last video from a playlist took away the whole action row,
so an owned server-side playlist could no longer be renamed or deleted
from the app at all. The menu stays; only what needs videos to act on —
play, download, save to library — goes.

Yattee/Localizable.xcstrings

@@ -8262,16 +8262,6 @@
         }
       }
     },
-    "playlist.empty.title" : {
-      "localizations" : {
-        "en" : {
-          "stringUnit" : {
-            "state" : "translated",
-            "value" : "Empty Playlist"
-          }
-        }
-      }
-    },
     "playlist.imported.title" : {
       "comment" : "Toast title when playlist is imported to library",
       "localizations" : {
@@ -8618,6 +8608,28 @@
         }
       }
     },
+    "playlists.selector.empty.account" : {
+      "comment" : "Shown in the playlist picker when an account has no playlists",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "No playlists on this account yet."
+          }
+        }
+      }
+    },
+    "playlists.selector.empty.local" : {
+      "comment" : "Shown in the playlist picker when there are no playlists on this device",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "No playlists on this device yet."
+          }
+        }
+      }
+    },
     "playlists.title" : {
       "comment" : "Title for playlists tab in instance browse",
       "localizations" : {