feat(Dialog): add fullHeight & fix styles on large heights

[zettca]

• add fullHeight prop to make it easier to build full-height Dialogs
  • very useful to prevent layout shifts in "complex" dialogs
  • currently user has to do classes={{paper: "w-full"}}, which is a bit obscure
• fix styles when HvDialog is larger/100%
  • Title/Actions is flexing, instead of content
• fix Title styles when custom children content
• make HvDialogActions using HvDialog's backgroundColor
• apply new props/fixes to the Form example & use it in Chromatic
• align chevron icon usage (Down -> DropDownXS)
• fix section border