Introduce a new StreamingEditFileTool (#29733)

This pull request introduces a new tool for streaming edits. The
short-term goal is for this tool to replace the existing `EditFileTool`,
but we want to get this out the door as soon as possible so that we can
start testing it.

`StreamingEditFileTool` is mutually exclusive with `EditFileTool`. It
will be enabled by default for anyone who has the `agent-stream-edits`
feature flag, as well as people that set `assistant.stream_edits` to
`true` in their settings.

### Implementation

Streaming is achieved by requesting a completion while the `edit_file`
tool gets called. We invoke the model by taking the existing
conversation with the agent and appending a prompt specifically tailored
for editing. In that prompt, we ask the model to produce a stream of
`<old_text>`/`<new_text>` tags. As the model streams text in, we
incrementally parse it and start editing as soon as we can.

### Evals

Note that, as part of this pull request, I also defined some new evals
that I used to drive the behavior of the recursive LLM call. To run
them, use this command:

```bash
cargo test --package=assistant_tools --features eval -- eval_extract_handle_command_output
```

Or comment out the `#[cfg_attr(not(feature = "eval"), ignore)]` macro.

I recommend running them one at a time, because right now we don't
really have a way of orchestrating of all these evals. I think we should
invest into that effort once the new agent panel goes live.

Release Notes:

- N/A

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>
Co-authored-by: Oleksiy Syvokon <oleksiy.syvokon@gmail.com>

Cargo.lock

@@ -704,7 +704,9 @@ dependencies = [
 name = "assistant_tools"
 version = "0.1.0"
 dependencies = [
+ "aho-corasick",
  "anyhow",
+ "assistant_settings",
  "assistant_tool",
  "buffer_diff",
  "chrono",
@@ -712,25 +714,36 @@ dependencies = [
  "clock",
  "collections",
  "component",
+ "derive_more",
  "editor",
+ "feature_flags",
+ "fs",
  "futures 0.3.31",
  "gpui",
+ "gpui_tokio",
+ "handlebars 4.5.0",
  "html_to_markdown",
  "http_client",
  "indoc",
  "itertools 0.14.0",
  "language",
  "language_model",
+ "language_models",
  "linkme",
  "open",
  "pretty_assertions",
  "project",
  "rand 0.8.5",
  "regex",
+ "reqwest_client",
+ "rust-embed",
  "schemars",
  "serde",
  "serde_json",
  "settings",
+ "smallvec",
+ "streaming_diff",
+ "strsim",
  "task",
  "tempfile",
  "terminal",
@@ -5003,6 +5016,7 @@ dependencies = [
  "node_runtime",
  "pathdiff",
  "paths",
+ "pretty_assertions",
  "project",
  "prompt_store",
  "regex",
@@ -6367,6 +6381,7 @@ dependencies = [
  "log",
  "pest",
  "pest_derive",
+ "rust-embed",
  "serde",
  "serde_json",
  "thiserror 1.0.69",
@@ -18032,6 +18047,7 @@ dependencies = [
  "getrandom 0.2.15",
  "getrandom 0.3.2",
  "gimli",
+ "handlebars 4.5.0",
  "hashbrown 0.14.5",
  "hashbrown 0.15.2",
  "heck 0.4.1",