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>

crates/assistant_tools/Cargo.toml

@@ -11,16 +11,24 @@ workspace = true
 [lib]
 path = "src/assistant_tools.rs"
 
+[features]
+eval = []
+
 [dependencies]
+aho-corasick.workspace = true
 anyhow.workspace = true
 assistant_tool.workspace = true
+assistant_settings.workspace = true
 buffer_diff.workspace = true
 chrono.workspace = true
 collections.workspace = true
 component.workspace = true
 editor.workspace = true
+derive_more.workspace = true
+feature_flags.workspace = true
 futures.workspace = true
 gpui.workspace = true
+handlebars = { workspace = true, features = ["rust-embed"] }
 html_to_markdown.workspace = true
 http_client.workspace = true
 indoc.workspace = true
@@ -31,9 +39,14 @@ linkme.workspace = true
 open.workspace = true
 project.workspace = true
 regex.workspace = true
+rust-embed.workspace = true
 schemars.workspace = true
 serde.workspace = true
 serde_json.workspace = true
+settings.workspace = true
+smallvec.workspace = true
+streaming_diff.workspace = true
+strsim.workspace = true
 task.workspace = true
 terminal.workspace = true
 terminal_view.workspace = true
@@ -49,10 +62,15 @@ client = { workspace = true, features = ["test-support"] }
 clock = { workspace = true, features = ["test-support"] }
 collections = { workspace = true, features = ["test-support"] }
 gpui = { workspace = true, features = ["test-support"] }
+gpui_tokio.workspace = true
+fs = { workspace = true, features = ["test-support"] }
 language = { workspace = true, features = ["test-support"] }
+language_model = { workspace = true, features = ["test-support"] }
+language_models.workspace = true
 project = { workspace = true, features = ["test-support"] }
 rand.workspace = true
 pretty_assertions.workspace = true
+reqwest_client.workspace = true
 settings = { workspace = true, features = ["test-support"] }
 task = { workspace = true, features = ["test-support"]}
 tempfile.workspace = true