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/vim/src/vim_test_context.rs

@@ -23,7 +23,10 @@ impl<'a> VimTestContext<'a> {
         cx.update(|cx| {
             editor::init(cx);
             crate::init(cx);
+
+            settings::keymap_file::load_built_in_keymaps(cx);
         });
+
         let params = cx.update(WorkspaceParams::test);
 
         cx.update(|cx| {