Change Granite.STYLE_CLASS_FOO to Granite.CssClass.FOO

### Problem

We used to use these C style constant names to match GTK, but they were all removed from GTK so there’s no need to do that anymore

### Proposal

- [x] Add either `Granite.StyleClass.FOO` or `Granite.CssClass.Foo` since these are used with `Gtk.Widget.add_css_class ()`

Mark Deprecated:
- [x] STYLE_CLASS_ACCENT
- [x] STYLE_CLASS_BACK_BUTTON
- [x] STYLE_CLASS_CARD
- [x] STYLE_CLASS_CHECKERBOARD
- [x] STYLE_CLASS_DESTRUCTIVE_ACTION
- [x] STYLE_CLASS_DIALOG_CONTENT_AREA
- [x] STYLE_CLASS_H1_LABEL
- [x] STYLE_CLASS_H2_LABEL
- [x] STYLE_CLASS_H3_LABEL
- [x] STYLE_CLASS_H4_LABEL
- [x] STYLE_CLASS_SUCCESS
- [x] STYLE_CLASS_TITLE_LABEL
- [x] STYLE_CLASS_LINKED
- [x] STYLE_CLASS_DIM_LABEL
- [x] STYLE_CLASS_ERROR
- [x] STYLE_CLASS_MESSAGE_DIALOG
- [x] STYLE_CLASS_RICH_LIST
- [x] STYLE_CLASS_SUGGESTED_ACTION
- [x] STYLE_CLASS_WARNING

- [x] STYLE_CLASS_CIRCULAR
- [x] STYLE_CLASS_SMALL_LABEL
- [x] STYLE_CLASS_MODE_SWITCH
- [x] STYLE_CLASS_WARMTH
- [x] STYLE_CLASS_TEMPERATURE
- [ ] STYLE_CLASS_BACKGROUND
- [ ] STYLE_CLASS_BADGE
- [ ] STYLE_CLASS_COLOR_BUTTON
- [ ] STYLE_CLASS_DEFAULT_DECORATION
- [x] STYLE_CLASS_FRAME
- [x] STYLE_CLASS_KEYCAP
- [ ] STYLE_CLASS_LARGE_ICONS
- [ ] STYLE_CLASS_OSD
- [x] STYLE_CLASS_ROUNDED
- [ ] STYLE_CLASS_SIDEBAR
- [ ] STYLE_CLASS_TERMINAL
- [x] STYLE_CLASS_MENU
- [x] STYLE_CLASS_MENUITEM
- [ ] STYLE_CLASS_FLAT
- [ ] STYLE_CLASS_VIEW

### Prior Art (Optional)

_No response_