TitleSubtitle Title Accessiblity

Ignore the label item for the purposes of accessibility.

This is another one coming up for the desire to make this work with FormCard (see libraries/kirigami-addons!229 (comment 912858)). This obviously means that this would only work with components that have a text property which is the primary use case for this in ItemDelegate (it'll also work in anything AbstractButton based). This would mean that it would only work in a Control based component if text was re implemented.

We need to do something here anyway as we don't want the title appearing in accessibility interfaces twice, other options would be to expose as a property or give the root component to this similar to SubtitleContentItem in Kirigami-addons Delegates.