Create an async Rust runtime with EventLoop

This is the API I'm envisioning Rust applications using. It doesn't have
everything wrapped yet, but it's enough to write some tests. It also
doesn't have an API managing the types like the C++ templates yet.

Change-Id: I3389cf18ea99f18c14dc8c4e732156d3cf8c8012
Signed-off-by: Brian Silverman <bsilver16384@gmail.com>
diff --git a/tools/lint/rustfmt.sh b/tools/lint/rustfmt.sh
index 42bb654..8539101 100755
--- a/tools/lint/rustfmt.sh
+++ b/tools/lint/rustfmt.sh
@@ -23,5 +23,5 @@
 
 # If we have any Rust files, format them.
 if ((${#rust_files[@]} > 0)); then
-    exec "${RUSTFMT}" "${rust_files[@]}"
+    exec "${RUSTFMT}" --edition=2021 "${rust_files[@]}"
 fi