Merge Efl.Orient and Efl.Flip into the same enum

Merge Efl.Orient and Efl.Flip into the same enum

Summary:
This is similar to how it is in Evas, and simplifies the Efl.Orientation
interface, which only needs one property now.

Relates to T7919

Test Plan: Everything builds and tests pass. There's only one example of efl_orientation_set() so there's not much to test yet.

Reviewers: zmike, bu5hm4n, cedric, Hermet, Jaehyun_Cho

Reviewed By: zmike

Subscribers: #reviewers, #committers

Tags: #efl

Maniphest Tasks: T7919

Differential Revision: https://phab.enlightenment.org/D8912