Converts an array of slot names into a SlotNamesMap.
Slot names that start with the element's tag name pass through unchanged. Slot names that do not
are transformed into the legacy ${tagName}-slot-${name} format so existing elements that
pre-date the tag prefix convention keep working.
Converts an array of slot names into a SlotNamesMap.
Slot names that start with the element's tag name pass through unchanged. Slot names that do not are transformed into the legacy
${tagName}-slot-${name}format so existing elements that pre-date the tag prefix convention keep working.