[EuiAccordion] Export underlying `EuiAccordionClass`?

[thompsongl]

The EuiAccordion export was changed from a class component to a function component during the move to Emotion styling. Functionally everything remains intact because of forwardRef, but the types no longer align: https://github.com/elastic/kibana/pull/133927#discussion_r901951296

We need to investigate a workaround or an additional top-level export that can be used instances where TypeScript needs access to the underlying class component.

Potentially as simple as exporting EuiAccordionClass.