[Embeddables] Extra type safety

[stacey-gammon]

It'd be great to get the input and output shapes typed correctly based on the type of embeddable so we get more type safety and don't have to cast. Especially when EmbeddableFactoryRenderer is introduced, this lacks type safety and input shape can be mismatched to the type passed in. I think we can do something similar to how the data search services does this with the request and response shapes mapped by search type.

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[ppisljar]

Thank you for contributing to this issue, however, we are closing this issue due to inactivity as part of a backlog grooming effort. If you believe this feature/bug should still be considered, please reopen with a comment.