patch 9.0.1725: cursor pos wrong after concealed text with 'virtualedit'

patch 9.0.1725: cursor pos wrong after concealed text with 'virtualedit'

Problem:    Wrong cursor position when clicking after concealed text
            with 'virtualedit'.
Solution:   Store virtual columns in ScreenCols[] instead of text
            columns, and always use coladvance() when clicking.

This also fixes incorrect curswant when clicking on a TAB, so now
Test_normal_click_on_ctrl_char() asserts the same results as the ones
before patch 9.0.0048.

closes: #12808

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>