Summary:
This diff contains several tight to each other changes (which can/should not be split into several diffs):
* The props parsing/conversion process was de-virtualized: we don't use virtual `apply` method to parse props anymore. Instead, we use old-fashioned constructors.
* All fields of Props classes which represent props values were marked as `const` which make impossible to modify them after the objects were created (even if we have non-const value-of/pointer-to the whole Props object). Those fields are also `public` now.
* All custom handwritten getters were removed (because we don't need them anymore).
So, now we don't need all those custom getters which makes code much more compact, performant and codegen-friendly.
Reviewed By: fkgozali
Differential Revision: D7901245
fbshipit-source-id: 9f4b1fd2da64bf963b63215ed3bd74b9d3c58dd5
dd3a6eda70