[mlir][async] Fix missing dialect dependency in async-to-async-runtime

[rkayaith]

Summary

The specific case I hit this was when lowering an async.execute that's
not inside a func.func op, e.g.:

llvm.func @foo() {
  %token = async.execute {
    async.yield
  }
  llvm.return
}

mlir/include/mlir/Dialect/Async/Passes.td

def AsyncToAsyncRuntime : Pass<"async-to-async-runtime", "ModuleOp"> {
   let constructor = "mlir::createAsyncToAsyncRuntimePass()";
   let options = [
     // Temporary for bringup, should become the default.
     Option<"eliminateBlockingAwaitOps", "eliminate-blocking-await-ops", "bool",
             /*default=*/"false",
            "Rewrite functions with blocking async.runtime.await as coroutines "
            "with async.runtime.await_and_resume.">,
   ];
-  let dependentDialects = ["async::AsyncDialect"];
+  let dependentDialects = ["async::AsyncDialect", "func::FuncDialect"];
 }
 
 def AsyncRuntimeRefCounting : Pass<"async-runtime-ref-counting"> {
   let summary = "Automatic reference counting for Async runtime operations";
   let description = [{
     This pass works at the async runtime abtraction level, after all
     `async.execute` and `async.await` operations are lowered to the async
     runtime API calls, and async coroutine operations.