Restructure react default props merging in order to enable easier server component checking
Restructure react default props merging in order to enable easier server component checking

Summary: In the next diff, I need to flow each of these properties to `React.TransportValue`. Without this diff, I would use `Property.read_t` on a `Neutral` property and always get back a `Some t`. In order to avoid unnecessary casing and exception handling, I pushed the part where we transform the types into properties to later in the function

Reviewed By: panagosg7

Differential Revision: D25133389

fbshipit-source-id: dea9b177e0222f9fb57ddf7a9d9e11a1eaa89d4b

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow