Adjust module organization to facilitate resurrection of the playground.

The playground doesn't / cannot depend on aiken-project because that becomes a gigantic pain. So instead, we try to keep essential stuff inside aiken-lang when possible.

crates/aiken-lang/src/utils/indexmap.rs

@@ -0,0 +1,21 @@
+use indexmap::IndexMap;
+use std::{collections::HashMap, hash::Hash};
+
+pub fn as_ref_values<'a, K, V>(iter: &'a IndexMap<K, V>) -> IndexMap<&'a K, &'a V>
+where
+    K: Eq + Hash + Clone + 'a,
+{
+    let mut refs = IndexMap::new();
+    for (k, v) in iter {
+        refs.insert(k, v);
+    }
+    refs
+}
+
+pub fn as_str_ref_values<V>(iter: &'_ HashMap<String, V>) -> IndexMap<&'_ str, &'_ V> {
+    let mut refs = IndexMap::new();
+    for (k, v) in iter {
+        refs.insert(k.as_str(), v);
+    }
+    refs
+}

crates/aiken-lang/src/utils/mod.rs

@@ -0,0 +1 @@
+pub mod indexmap;