Combine zeta and zeta2 edit prediction providers (#43284)

We've realized that a lot of the logic within an
`EditPredictionProvider` is not specific to a particular edit prediction
model / service. Rather, it is just the generic state management
required to perform edit predictions at all in Zed. We want to move to a
setup where there's one "built-in" edit prediction provider in Zed,
which can be pointed at different edit prediction models. The only logic
that is different for different models is how we construct the prompt,
send the request, and parse the output.

This PR also changes the behavior of the staff-only `zeta2` feature flag
so that in only gates your *ability* to use Zeta2, but you can still use
your local settings file to choose between different edit prediction
models/services: zeta1, zeta2, and sweep.

This PR also makes zeta1's outcome reporting and prediction-rating
features work with all prediction models, not just zeta1.

To do:
* [x] remove duplicated logic around sending cloud requests between
zeta1 and zeta2
* [x] port the outcome reporting logic from zeta to zeta2.
* [x] get the "rate completions" modal working with all EP models
   * [x] display edit prediction diff
   * [x] show edit history events
* [x] remove the original `zeta` crate.

Release Notes:

- N/A

---------

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

crates/cloud_llm_client/src/predict_edits_v3.rs

@@ -3,7 +3,7 @@ use serde::{Deserialize, Serialize};
 use std::{
     fmt::{Display, Write as _},
     ops::{Add, Range, Sub},
-    path::{Path, PathBuf},
+    path::Path,
     sync::Arc,
 };
 use strum::EnumIter;
@@ -17,7 +17,7 @@ pub struct PlanContextRetrievalRequest {
     pub excerpt_path: Arc<Path>,
     pub excerpt_line_range: Range<Line>,
     pub cursor_file_max_row: Line,
-    pub events: Vec<Event>,
+    pub events: Vec<Arc<Event>>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -36,7 +36,7 @@ pub struct PredictEditsRequest {
     pub signatures: Vec<Signature>,
     #[serde(skip_serializing_if = "Vec::is_empty", default)]
     pub referenced_declarations: Vec<ReferencedDeclaration>,
-    pub events: Vec<Event>,
+    pub events: Vec<Arc<Event>>,
     #[serde(default)]
     pub can_collect_data: bool,
     #[serde(skip_serializing_if = "Vec::is_empty", default)]
@@ -120,10 +120,11 @@ impl std::fmt::Display for PromptFormat {
 #[serde(tag = "event")]
 pub enum Event {
     BufferChange {
-        path: Option<PathBuf>,
-        old_path: Option<PathBuf>,
+        path: Arc<Path>,
+        old_path: Arc<Path>,
         diff: String,
         predicted: bool,
+        in_open_source_repo: bool,
     },
 }
 
@@ -135,23 +136,21 @@ impl Display for Event {
                 old_path,
                 diff,
                 predicted,
+                ..
             } => {
-                let new_path = path.as_deref().unwrap_or(Path::new("untitled"));
-                let old_path = old_path.as_deref().unwrap_or(new_path);
-
                 if *predicted {
                     write!(
                         f,
                         "// User accepted prediction:\n--- a/{}\n+++ b/{}\n{diff}",
                         DiffPathFmt(old_path),
-                        DiffPathFmt(new_path)
+                        DiffPathFmt(path)
                     )
                 } else {
                     write!(
                         f,
                         "--- a/{}\n+++ b/{}\n{diff}",
                         DiffPathFmt(old_path),
-                        DiffPathFmt(new_path)
+                        DiffPathFmt(path)
                     )
                 }
             }
@@ -300,10 +299,11 @@ mod tests {
     #[test]
     fn test_event_display() {
         let ev = Event::BufferChange {
-            path: None,
-            old_path: None,
+            path: Path::new("untitled").into(),
+            old_path: Path::new("untitled").into(),
             diff: "@@ -1,2 +1,2 @@\n-a\n-b\n".into(),
             predicted: false,
+            in_open_source_repo: true,
         };
         assert_eq!(
             ev.to_string(),
@@ -317,10 +317,11 @@ mod tests {
         );
 
         let ev = Event::BufferChange {
-            path: Some(PathBuf::from("foo/bar.txt")),
-            old_path: Some(PathBuf::from("foo/bar.txt")),
+            path: Path::new("foo/bar.txt").into(),
+            old_path: Path::new("foo/bar.txt").into(),
             diff: "@@ -1,2 +1,2 @@\n-a\n-b\n".into(),
             predicted: false,
+            in_open_source_repo: true,
         };
         assert_eq!(
             ev.to_string(),
@@ -334,10 +335,11 @@ mod tests {
         );
 
         let ev = Event::BufferChange {
-            path: Some(PathBuf::from("abc.txt")),
-            old_path: Some(PathBuf::from("123.txt")),
+            path: Path::new("abc.txt").into(),
+            old_path: Path::new("123.txt").into(),
             diff: "@@ -1,2 +1,2 @@\n-a\n-b\n".into(),
             predicted: false,
+            in_open_source_repo: true,
         };
         assert_eq!(
             ev.to_string(),
@@ -351,10 +353,11 @@ mod tests {
         );
 
         let ev = Event::BufferChange {
-            path: Some(PathBuf::from("abc.txt")),
-            old_path: Some(PathBuf::from("123.txt")),
+            path: Path::new("abc.txt").into(),
+            old_path: Path::new("123.txt").into(),
             diff: "@@ -1,2 +1,2 @@\n-a\n-b\n".into(),
             predicted: true,
+            in_open_source_repo: true,
         };
         assert_eq!(
             ev.to_string(),