efl.canvas.textblock: update style strings

efl.canvas.textblock: update style strings

Summary:
Update

backing -> background_type
backing_color -> background_color
underline_dash_color -> underline_dashed_color
underline - > underline_type
strikethrough - > strikethrough_type
style -> (effect_type + shadow_direction)
underline_dash_width -> underline_dashed_width
underline_dashed_gap -> underline_dashed_gap

**+prevent unified APIs from supporting legacy style tags, and prevent legacy APIs from the ability to use new unified tags**

Reviewers: zmike, woohyun, segfaultxavi, bu5hm4n, cedric

Reviewed By: segfaultxavi, bu5hm4n

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Maniphest Tasks: T8523

Differential Revision: https://phab.enlightenment.org/D11188