Implement tuple type parsing

Also change some tests with newly relaxed indentation requirements, and remove an irrelevant test (since unindented close parens are now perfectly valid, the test is no longer useful).

crates/compiler/parse/src/ast.rs

@@ -527,6 +527,13 @@ pub enum TypeAnnotation<'a> {
         ext: Option<&'a Loc<TypeAnnotation<'a>>>,
     },
 
+    Tuple {
+        fields: Collection<'a, Loc<TypeAnnotation<'a>>>,
+        /// The row type variable in an open record, e.g. the `r` in `{ name: Str }r`.
+        /// This is None if it's a closed record annotation like `{ name: Str }`.
+        ext: Option<&'a Loc<TypeAnnotation<'a>>>,
+    },
+
     /// A tag union, e.g. `[
     TagUnion {
         /// The row type variable in an open tag union, e.g. the `a` in `[Foo, Bar]a`.