Cleanup temporary directories in model editor

[koesie10]

This cleans up the two temporary directories we create in the model editor:

• When opening the model editor, a temporary directory with the query files is created. This will clean it up after either the panel or the view is disposed. This is just temporary, the queryDir will be removed once the queries have been moved to github/codeql.
• When using the automodel functionality, a temporary directory with an extension pack containing the filter is created. This will clean it up after running the query.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[robertbrignull]

Looks good to me.

We could make use of some try { ... } finally { ... } blocks, but I'm not sure it's worth it. As far as I can tell, we're using tmp dirs so they'll be deleted when the computer is restarted.