Files section: allow defining upload template, when `query`

[distantnative]

Currently, it is not possible to filter files via query to include a set of files with different templates but also to define what template an upload should receive. Setting the template option will further filter down the set of files.

https://forum.getkirby.com/t/files-section-with-query-and-uploads-template/32571

[distantnative]

@getkirby/staff I would be interested to get your opinions on which of these two options to pursue:

a) Use template option to always assign the template for new uploads. In turn, when query is used, don't filter set of files further down by template (breaking change for those who currently rely on their set of files being filtered by query and template).

b) Add a new uploads option with subkey template. Downside would be handling of supporting template and uploads.template together.