Set DetailsSummary slot by default

[sissbruecker]

To assign a custom DetailsSummary in Details you need write:

<Details>
  <DetailsSummary slot="summary">foo</DetailsSummary>
</Details>

The slot="summary" seems redundant, as this is the only place where a details summary should be used. Instead, the component could set the slot by default. We could also consider doing this for the web component itself.

AccordionSummary could also be updated to use the same approach.

[web-padawan]

In case of the web component, we need some kind of named slot to distinguish summary from the content.
However, similar improvement could be done for the Tooltip so that we don't need to set slot="tooltip".