Make field declarations a source for completion identifiers

This only returns field identifiers which are in the current scope.
If a field declaration is in scope, it means that we have access to
it and we should include it as a possible completion identiifer.

lsp/nls/src/requests/completion.rs

@@ -561,7 +561,8 @@ fn get_completion_identifiers(
                     .get_in_scope(item, &server.lin_cache)
                     .iter()
                     .filter_map(|i| match i.kind {
-                        TermKind::Declaration(ident, _, _) => Some(IdentWithType {
+                        TermKind::Declaration(ident, _, _)
+                        | TermKind::RecordField { ident, .. } => Some(IdentWithType {
                             ident,
                             item: Some(item.clone()),
                             ty: ty.clone(),