Label slot on sl-input

[tstewart-klaudhaus]

Is your feature request related to a problem? Please describe.
It would be great to specify custom content as the label of an input (and maybe other similar labelled components) e.g. in order to add an icon with tooltip for more information, or an tag to link out to somewhere else, or to have text formatting within the label, etc.

Describe the solution you'd like
If label were a slot, we could customise it in this way. Similar to how we can customise the summary of sl-detail instead of choosing to specify it as a text property.

Describe alternatives you've considered
Thought about using css ::after, but only allows simple content not HTML.

Ended up removing label from input and placing it within a div with my custom label content above.