Fix strange behavior with list close tags and empty list tags

[Rindbee]

Fix the first two points in #61621.

Support for two writing ways: compact or loose. The loose one is designed for easy editing in the editor. For this, the first blank line (if exists) right after the list tags ([ol], [/ol], [ul], and [/ul]) will be ignored.

Make sure the empty list contains at least one item, that is, an empty list is ultimately a list with one item. As a reminder here is a list.

test 1

a[ol][/ol]b
a
[ol][/ol]
b
a
[ol]
[/ol]
b
a
[ol]

[/ol]
b
a
[ol]


[/ol]
b

test 2

a
[ol]text[/ol]
b
a[ol]text[/ol]b
a[ol]text
[/ol]b
a[ol]
text[/ol]b
a[ol]
text
[/ol]b
a[ol]

text
[/ol]b
a[ol]

text

[/ol]b

test 3

a
b[ol]
[ul]
text
[/ul]
[/ol]c
d
a[ol][color=red]red[/color]text[color=red]red[/color][ul][color=green]green[/color]text[color=green]green[/color][/ul][/ol]b
a
[ol]
[color=red]red[/color]text[color=red]red[/color]
[ul]
[color=green]green[/color]text[color=green]green[/color]
[/ul]
[/ol]
b
a
[ol]
[color=red]red[/color]
text
[color=red]red[/color]
[ul]
[color=green]green[/color]
text
[color=green]green[/color]
[/ul]
[/ol]
b

[akien-mga]

Thanks!