zeta2: Provider setup (#38676)

Creates a new `EditPredictionProvider` for zeta2, that requests
completions from a new cloud endpoint including context from the new
`edit_prediction_context` crate. This is not ready for use, but it
allows us to iterate.

Release Notes:

- N/A

---------

Co-authored-by: Michael Sloan <michael@zed.dev>
Co-authored-by: Bennet <bennet@zed.dev>
Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>

crates/settings/src/settings_content/language.rs

@@ -84,6 +84,17 @@ pub enum EditPredictionProvider {
     Zed,
 }
 
+impl EditPredictionProvider {
+    pub fn is_zed(&self) -> bool {
+        match self {
+            EditPredictionProvider::Zed => true,
+            EditPredictionProvider::None
+            | EditPredictionProvider::Copilot
+            | EditPredictionProvider::Supermaven => false,
+        }
+    }
+}
+
 /// The contents of the edit prediction settings.
 #[skip_serializing_none]
 #[derive(Clone, Debug, Default, Serialize, Deserialize, JsonSchema, MergeFrom, PartialEq)]