Move assets to their own crate, load keymaps in vim tests

Also, move assets folder to the top-level.

Co-authored-by: Keith Simmons <keith@zed.dev>

crates/zed/src/test.rs

@@ -1,4 +1,5 @@
-use crate::{assets::Assets, build_window_options, build_workspace, AppState};
+use crate::{build_window_options, build_workspace, AppState};
+use assets::Assets;
 use client::{test::FakeHttpClient, ChannelList, Client, UserStore};
 use gpui::MutableAppContext;
 use language::LanguageRegistry;