feat(HelpButton): Add inline display variant

[Sundfjord]

This PR will add a new variant of the HelpButton component, that displays its contents in an inline element, as so:

The help content container will by default be appended to the HelpButton instance's parent element, but a contentId may also be specified to place the help content container in any existing DOM element.

In addition to the necessary changes in the HelpButton component, FormLabel now accepts a new help prop which will by default display what is sent with the contents prop in an inline help button. The changes to the component are mainly done to ensure correct positioning of both the help button itself and its contents regardless of label direction.

Test cases have been added for this new variant.