Redo jumbotron padding

Fixes #16374 (closed).

• In general, there are very few instances that would require a jumbotron without a parent or child container.
• Right now we account for that behavior though with some horizontal padding on the .jumbotron class.
• This removes that horizontal padding as it narrows our grid classes unnecessarily and accounts for a super small use case.
• It also improves consistency across breakpoints, in that padding isn't being added and removed.
• In doing so, I also removed the shorthand padding property and went with the specific ones (because yay specificity).

/cc @rlindner81