[Layout] Add more default layout options

[qgib]

Author Name: Harrissou Santanna (@DelazJ)
Original Redmine Issue: 19022

Redmine category:map_composer/printing

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In the Settings --> Options dialog there is a "Print layout" tab you can use to configure some default values for any new print layout.
I think we should really improve these features with adding some items such as:

• Page size (i can not recall the last time I use A4 format, but it's the default, hence i have to change it each time)
• Layout dpi: by default, it's 300 (too much for me). Could be nice to have it changed at a single page instead of having to change it at each export
• the atlas raster format to export to
• I'd say default font size, given that there's a default font (which btw is not applied to new layouts)
• ... others?...