* Initial working fixed ironing angle implemented with new Fixed ironing angle setting
* update documentation
* Combine Fill.is_using_template_angle and Fill.alternate_fill_direction into Fill.fixed_angle
* Rename SurfaceFillParams.is_using_template_angle to SurfaceFillParam.fixed_angle.
* Change ironing angle setting to be an offset angle from the top surface angle rather offset from the layer 0 angle that changes on each layer.
* Change Ironing angle offset range from [-1,359] to [0,359].
-1 is redundant because it is the same behavior as 0 offset.
* Change ironing_angle new default value to 0.
* Update existing print profiles' hardcoded ironing_angles from -1 to 0 to reflect new default value.
* Add migration for old -1 ironing_angle settings. Remove logic for -1 ironing_angle.
* Add u8 prefix for degree symbol string
* Use solid_infill_direction instead of infill_direction for top surface infill direction. Use calculate_infill_rotation_angle to add offset to solid_infill_rotate_template if used.
* Update quality settings wiki for Ironing
* Set f->is_using_template_angle when making ironing filler objects
* Update quality_settings_ironing link from #angle to #angle-offset
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Co-authored-by: Noisyfox <timemanager.rick@gmail.com>
