Summary:
Cleans up the native component configuration for `RCTText` and `RCTVirtualText`.
This //does// lead to a breaking change because `Text.viewConfig` will no longer exist. However, I think this is acceptable because `viewConfig` has already long stopped being an exported prop on other core components (e.g. `View`).
Changelog:
[General][Removed] - `Text.viewConfig` is no longer exported.
Reviewed By: shergin
Differential Revision: D23708205
fbshipit-source-id: 1ad0b0772735834d9162a65d9434a9bbbd142416