Improve edit prediction example capture (#45536)

This PR improves the `edit prediction: Capture Example` in several ways:
* fixed bugs in how the uncommitted diff was calculated
* added a `edit_predictions.examples_dir` setting that can be set in
order to have the action automatically save examples into the given
folder
* moved the action into the `edit_predictions` crate, in preparation for
collecting this data passively from end users, when they have opted in
to data sharing, similar to what we did for Zeta 1

Release Notes:

- N/A

Cargo.lock

@@ -5212,6 +5212,7 @@ dependencies = [
  "anyhow",
  "arrayvec",
  "brotli",
+ "buffer_diff",
  "client",
  "clock",
  "cloud_api_types",
@@ -5249,7 +5250,9 @@ dependencies = [
  "strum 0.27.2",
  "telemetry",
  "telemetry_events",
+ "text",
  "thiserror 2.0.17",
+ "time",
  "ui",
  "util",
  "uuid",
@@ -5354,8 +5357,10 @@ dependencies = [
  "anyhow",
  "buffer_diff",
  "client",
+ "clock",
  "cloud_llm_client",
  "codestral",
+ "collections",
  "command_palette_hooks",
  "copilot",
  "edit_prediction",
@@ -5364,18 +5369,20 @@ dependencies = [
  "feature_flags",
  "fs",
  "futures 0.3.31",
- "git",
  "gpui",
  "indoc",
  "language",
- "log",
+ "language_model",
  "lsp",
  "markdown",
  "menu",
  "multi_buffer",
  "paths",
+ "pretty_assertions",
  "project",
  "regex",
+ "release_channel",
+ "semver",
  "serde_json",
  "settings",
  "supermaven",
@@ -5388,6 +5395,7 @@ dependencies = [
  "workspace",
  "zed_actions",
  "zeta_prompt",
+ "zlog",
 ]
 
 [[package]]