assistant2: Decouple scripting tool from the Tool trait (#26382)

This PR decouples the scripting tool from the `Tool` trait while still
allowing it to be used as a tool from the model's perspective.

This will allow us to evolve the scripting tool as more of a first-class
citizen while still retaining the ability to have the model call it as a
regular tool.

Release Notes:

- N/A

Cargo.lock

@@ -490,6 +490,7 @@ dependencies = [
  "proto",
  "rand 0.8.5",
  "rope",
+ "scripting_tool",
  "serde",
  "serde_json",
  "settings",
@@ -11915,7 +11916,6 @@ name = "scripting_tool"
 version = "0.1.0"
 dependencies = [
  "anyhow",
- "assistant_tool",
  "collections",
  "futures 0.3.31",
  "gpui",
@@ -16986,7 +16986,6 @@ dependencies = [
  "repl",
  "reqwest_client",
  "rope",
- "scripting_tool",
  "search",
  "serde",
  "serde_json",