GSP code style: Space in empty tag

When autocompleting, I want to get a space character before the closing `/>` in an empty GSP tag

For HTML and XML tags there already seems to be an option for this in the settings.

I've attached a few screenshots to illustrate the problem.

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*Imported from [IDEA-134764](https://youtrack.jetbrains.com/issue/IDEA-134764) · Type: Feature · Votes: 0*
*Comments, attachments, dates and reporter are not part of the export — follow the link above for the full history.*

Start by finding the GSP tag-completion code and the existing HTML/XML setting for spacing before a closing />. Check how those settings affect autocomplete, then determine where GSP completion can follow the same behavior. Done when completing an empty GSP tag inserts a space before /> and the behavior is covered by an appropriate test.

Written by the indexing model from the issue text.