Add experimental mercury edit prediction provider (#44256)

Release Notes:

- N/A

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/zed/src/zed/edit_prediction_registry.rs

@@ -9,6 +9,7 @@ use gpui::{AnyWindowHandle, App, AppContext as _, Context, Entity, WeakEntity};
 use language::language_settings::{EditPredictionProvider, all_language_settings};
 use language_models::MistralLanguageModelProvider;
 use settings::{
+    EXPERIMENTAL_MERCURY_EDIT_PREDICTION_PROVIDER_NAME,
     EXPERIMENTAL_SWEEP_EDIT_PREDICTION_PROVIDER_NAME,
     EXPERIMENTAL_ZETA2_EDIT_PREDICTION_PROVIDER_NAME, SettingsStore,
 };
@@ -219,6 +220,10 @@ fn assign_edit_prediction_provider(
                             && cx.has_flag::<Zeta2FeatureFlag>()
                         {
                             edit_prediction::EditPredictionModel::Zeta2
+                        } else if name == EXPERIMENTAL_MERCURY_EDIT_PREDICTION_PROVIDER_NAME
+                            && cx.has_flag::<Zeta2FeatureFlag>()
+                        {
+                            edit_prediction::EditPredictionModel::Mercury
                         } else {
                             return false;
                         }