Inconsistent grid header padding in v7 themes #12306
Description
Hello there!
I noticed that Grid's header padding is inconsistently applied across various themes in v7.
Top padding is set to 0 in some themes, but not all, which leads to an inconsisten experience.
But that 0 top padding might be a mistake by itself as it does not make any sense.
Try for for yourself: go to any Grid example or open the Grid docs page, add a title config to the Grid class instance, and scroll through the different themes. You'll notice that in some cases the title bar has no spacing above the text (Svalbard Light and both Material3 themes), which I believe is a bug.
Many thanks!
