bug#60781: 28.2; column-number-mode counts differently based on character encoding

[Van Ly]

Hello,

// one right arrow key move of the cursor from the left most position
// numbers differently in column-number-mode based on character encoding

These steps reproduce the observed unexpected behavior:

* emacs -Q /tmp/example.text
* move cursor to line two at left most position, then right arrow key once
* M-x column-number-mode
* the modeline indicator shows (2,2)
* move cursor to line nine at left most position, then right arrow key once
* the modeline indicator shows (9,1)

// for cjk the column number is two
// for ascii the column number is one

* expected modeline indicator to show (2,1) and (9,1)

See attached: bug-report.text, example.text

bug-report.text
Description: bug report data

example.text
Description: example file to reproduce steps