Make multiline prompt invert-colored spaces.

[attah]

This way it is syntactically correct, as opposed to '..'.

Fixes #7558

I got only one failure in stdlib tests, which was in ssh, and seemed unrelated.
Maybe i missed where it was tested still somehow, or there were no tests.

[github-actions]

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[frazze-jobb]

Regarding test,
There are two occurances in kernel/src/interactive_shell_SUITE.erl
shell_multiline_navigation
shell_receive_standard_out

Nice idea with inverted colors!

[attah]

Aha! I was looking in stdlib where the change was. ...and seemingly tests here passed?
I had an initial look (with at least one failure), and let's just say i need to spend more time on it :)
I'm starting to doubt very much that the ".." in the test is actually matching literal "..", but just any two characters.

Thanks!
People tend to be particular with their terminal colors, so a relative color seemed safer than an absolute.

[attah]

I'm getting nowhere fast with this.
I only get a failure in "shell_receive_standard_out", and something about how it is testing breaks with the escape sequences.
My understanding is that it is testing that the newline (and newline indicator) remains where it should even after the fun has printed some stuff before it, while the user had not finished writing.
This works fine "IRL", but in the test the newline indicator is borked and incomplete:

0
1
2
3
4
(�[94m한국어/조선말�[39m)4> ABC
               �[7m  �[0m�[39m�[49m

Compared to the old output of:

0
1
2
3
4
(�[94m한국어/조선말�[39m)4> ABC
               ..

[frazze-jobb]

I will have a look