feat(ui): support native HTML attributes on Grid components

Extend GridProps and GridItemProps to accept standard HTML div
attributes by inheriting from React.HTMLAttributes<HTMLDivElement>.
The rest props are spread onto the underlying div elements.

Signed-off-by: Johan Persson <johanopersson@gmail.com>

.changeset/flex-html-attributes.md

@@ -1,7 +0,0 @@
----
-'@backstage/ui': patch
----
-
-Added support for native HTML div attributes on the `Flex` component.
-
-**Affected components:** Flex

.changeset/layout-html-attributes.md

@@ -0,0 +1,7 @@
+---
+'@backstage/ui': patch
+---
+
+Added support for native HTML div attributes on the `Flex`, `Grid`, and `Grid.Item` components.
+
+**Affected components:** Flex, Grid, Grid.Item