previously, if there was a newline in some variables, it would not format
properly in `xbps-src show`. This fixes it by always splitting it by word
in some cases, like if there is a new line in the variable's value, and
removing internal commas in some cases.
This logic was split into a function for consistency.
fixes#40996
Example:
```
$ ./xbps-src show keepassxc
pkgname: keepassxc
...
License(s): GPL-3.0-or-later
License(s): BSD-3-Clause
License(s): CC0-1.0
License(s): LGPL-2.0-only
License(s): LGPL-2.1-only
License(s): LGPL-3.0-or-later
License(s): Nokia-Qt-exception-1.1
License(s): MIT
License(s): BSL-1.0
```
7c8f15bf1b