Expose JPG encode quality in export settings

[atteneder]

Discussed in #658

^{Originally posted by Henkka-san November 21, 2023}
It seems that currently the JPG quality is hardcoded to 60%. It would be helpful if the compression level could be given when Export is requested.

[atteneder]

Context:
ImageConversion.EncodeToJPG

Setting at what granularity level?

1. Global/static setting
2. per-export setting
3. per texture type setting (basecolor, normal, ORM,...)
4. per texture setting/callback

I gravitate towards 2, but open for ideas.