Reorganize edit prediction code and remove old experiments (#44187)

Release Notes:

- N/A

---------

Co-authored-by: Agus Zubiaga <agus@zed.dev>
Co-authored-by: Ben Kunkle <ben@zed.dev>

assets/keymaps/default-linux.json

@@ -41,7 +41,7 @@
       "ctrl-f11": "debugger::StepInto",
       "shift-f11": "debugger::StepOut",
       "f11": "zed::ToggleFullScreen",
-      "ctrl-alt-z": "edit_prediction::RateCompletions",
+      "ctrl-alt-z": "edit_prediction::RatePredictions",
       "ctrl-alt-shift-i": "edit_prediction::ToggleMenu",
       "ctrl-alt-l": "lsp_tool::ToggleMenu"
     }
@@ -1322,18 +1322,10 @@
     }
   },
   {
-    "context": "Zeta2Feedback > Editor",
+    "context": "EditPredictionContext > Editor",
     "bindings": {
-      "enter": "editor::Newline",
-      "ctrl-enter up": "dev::Zeta2RatePredictionPositive",
-      "ctrl-enter down": "dev::Zeta2RatePredictionNegative"
-    }
-  },
-  {
-    "context": "Zeta2Context > Editor",
-    "bindings": {
-      "alt-left": "dev::Zeta2ContextGoBack",
-      "alt-right": "dev::Zeta2ContextGoForward"
+      "alt-left": "dev::EditPredictionContextGoBack",
+      "alt-right": "dev::EditPredictionContextGoForward"
     }
   },
   {