fix: preserve location information for `await` wrappers (#18859)

Helps with code coverage tools:
https://github.com/sveltejs/esrap/pull/124

.changeset/major-roses-help.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: preserve location information for `await` wrappers

packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitExpression.js

@@ -18,7 +18,8 @@ export function AwaitExpression(node, context) {
 	// in dev, note which values are read inside a reactive expression,
 	// but don't track them
 	else if (dev && !is_ignored(node, 'await_reactivity_loss')) {
-		return b.call(b.await(b.call('$.track_reactivity_loss', argument)));
+		// don't use b.await here, this way we preserve location information
+		return b.call({ ...node, argument: b.call('$.track_reactivity_loss', argument) });
 	}
 
 	return argument === node.argument ? node : { ...node, argument };