Add experimental LSP-based context retrieval system for edit prediction (#44036)

To do

* [x] Default to no context retrieval. Allow opting in to LSP-based
retrieval via a setting (for users in `zeta2` feature flag)
* [x] Feed this context to models when enabled
* [x] Make the zeta2 context view work well with LSP retrieval
* [x] Add a UI for the setting (for feature-flagged users)
* [x] Ensure Zeta CLI `context` command is usable

---

* [ ] Filter out LSP definitions that are too large / entire files (e.g.
modules)
* [ ] Introduce timeouts
* [ ] Test with other LSPs
* [ ] Figure out hangs

Release Notes:

- N/A

---------

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

Cargo.lock

@@ -5342,6 +5342,32 @@ dependencies = [
  "zlog",
 ]
 
+[[package]]
+name = "edit_prediction_context2"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "collections",
+ "env_logger 0.11.8",
+ "futures 0.3.31",
+ "gpui",
+ "indoc",
+ "language",
+ "log",
+ "lsp",
+ "parking_lot",
+ "pretty_assertions",
+ "project",
+ "serde",
+ "serde_json",
+ "settings",
+ "smallvec",
+ "text",
+ "tree-sitter",
+ "util",
+ "zlog",
+]
+
 [[package]]
 name = "editor"
 version = "0.1.0"
@@ -21693,6 +21719,7 @@ dependencies = [
  "db",
  "edit_prediction",
  "edit_prediction_context",
+ "edit_prediction_context2",
  "editor",
  "feature_flags",
  "fs",
@@ -21742,7 +21769,6 @@ dependencies = [
  "clap",
  "client",
  "cloud_llm_client",
- "cloud_zeta2_prompt",
  "collections",
  "edit_prediction_context",
  "editor",