assistant2: Order agent profiles in the order they are defined in settings (#27255)

This PR updates the ordering of the agent profiles in the tool selector
to respect the order they are defined in in the settings instead of
sorting them alphabetically.

This gives the user more control, and allows them to order the profiles
as they desire.

Release Notes:

- N/A

crates/assistant_settings/Cargo.toml

@@ -14,9 +14,9 @@ path = "src/assistant_settings.rs"
 [dependencies]
 anthropic = { workspace = true, features = ["schemars"] }
 anyhow.workspace = true
-collections.workspace = true
 feature_flags.workspace = true
 gpui.workspace = true
+indexmap.workspace = true
 language_model.workspace = true
 lmstudio = { workspace = true, features = ["schemars"] }
 log.workspace = true