evas_textblock: prevent updating cursor unless they are ready during markup_set
During Markup_set at text block level, we will not update the cursors, unless their status is updated and ready.
This can cause serious issues, especially if a cursor also depends on another cursor for some calculations, (like the segfault happening in TextBox T8637)
Reviewers: woohyun, bu5hm4n, zmike
Reviewed By: woohyun
Maniphest Tasks: T8637
Differential Revision: https://phab.enlightenment.org/D11598