Update various components to be callable

[querkmachine]

Updates various components to be callable.

Callers make it easier for users of the Design System to pass large amounts of HTML directly into a component, without having to first assign it to a variable and then pass it to the html parameter.

Suggested in #941, and based on the list of components I commented there, with some changes.

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I intend to make these components callable. In all situations, the called content will replace and take priority over the html and text parameters.

• Details
• Error summary (replacing the descriptionHtml and descriptionText parameters)
• Inset text
• Notification banner
• Panel

I'm no longer considering the following components:

• Cookie banner: This component accepts looping content to allow for segregating consent into multiple groups. This is incompatible with using a caller, which only supports one slot of called content per component.
• Warning text: The main text of this component is presented inside of a <strong> element, negating the usefulness of using a caller, as it's unlikely to ever be more than one line of text.

[domoscargin]

This looks good to me - and anecdotally would've been useful in my previous work using govuk-frontend!

I've left two small notes on the Changelog, which aren't blocking.

[domoscargin]

Looks grand!

[paulmsmith]

I have been manually doing this in my projects for quite a while (with a wrapper macro). This is brill!