fix: xonsh: Refactor space appending logic in action.go

[anki-code]

Hi! I've got the issue request from xonsh shell user but I see that the issue is on carapace side.

Before

exec($(carapace _carapace xonsh))
cd /tmp
mkdir -p 'foo bar/1/2'
ls foo<Tab>  # carapace
ls 'foo bar' <cursor>  # space after completion and next Tab is not working to go to subdirectory 🔴 

After

ls foo<Tab>  # carapace
ls 'foo bar'<cursor>  #  no space after completion and next Tab is working to go to dubdirectory 🟢 
ls 'foo bar/1'

Fix

Decide whether a trailing space is wanted BEFORE wrapping the value in quotes. Nospace is a SuffixMatcher and inspects the last rune of the value (e.g. "/" for directories, "=" for flags expecting a value). If we ran this check after quoting, the value would end with "'" and the match would always fail, causing a trailing space to be appended for paths like "foo bar/" -- the cursor would land after the space and tab completion of the next path part would be impossible.