feat: add create_index to the async python API (#1052)

This also refactors the rust lancedb index builder API (and,
correspondingly, the nodejs API)

python/src/util.rs

@@ -0,0 +1,35 @@
+use std::sync::Mutex;
+
+use pyo3::{exceptions::PyRuntimeError, PyResult};
+
+/// A wrapper around a rust builder
+///
+/// Rust builders are often implemented so that the builder methods
+/// consume the builder and return a new one. This is not compatible
+/// with the pyo3, which, being garbage collected, cannot easily obtain
+/// ownership of an object.
+///
+/// This wrapper converts the compile-time safety of rust into runtime
+/// errors if any attempt to use the builder happens after it is consumed.
+pub struct BuilderWrapper<T> {
+    name: String,
+    inner: Mutex<Option<T>>,
+}
+
+impl<T> BuilderWrapper<T> {
+    pub fn new(name: impl AsRef<str>, inner: T) -> Self {
+        Self {
+            name: name.as_ref().to_string(),
+            inner: Mutex::new(Some(inner)),
+        }
+    }
+
+    pub fn consume<O>(&self, mod_fn: impl FnOnce(T) -> O) -> PyResult<O> {
+        let mut inner = self.inner.lock().unwrap();
+        let inner_builder = inner.take().ok_or_else(|| {
+            PyRuntimeError::new_err(format!("{} has already been consumed", self.name))
+        })?;
+        let result = mod_fn(inner_builder);
+        Ok(result)
+    }
+}