Extract paths out of util (#13182)

This PR extracts the definition of the various Zed paths out of `util`
and into a new `paths` crate.

`util` is for generic utils, while these paths are Zed-specific. For
instance, `gpui` depends on `util`, and it shouldn't have knowledge of
these paths, since they are only used by Zed.

Release Notes:

- N/A

crates/assistant/src/assistant.rs

@@ -21,6 +21,7 @@ pub(crate) use context_store::*;
 use gpui::{actions, AppContext, Global, SharedString, UpdateGlobal};
 pub(crate) use inline_assistant::*;
 pub(crate) use model_selector::*;
+use paths::EMBEDDINGS_DIR;
 use rustdoc::RustdocStore;
 use semantic_index::{CloudEmbeddingProvider, SemanticIndex};
 use serde::{Deserialize, Serialize};
@@ -34,7 +35,6 @@ use std::{
     sync::Arc,
 };
 pub(crate) use streaming_diff::*;
-use util::paths::EMBEDDINGS_DIR;
 
 actions!(
     assistant,