Support for multiple Format= in a single image

[NekkoDroid]

This would be useful to be able to use a single configuration for building a distributable raw disk image and a tar file to use as as base tree for further sysext/confext.

This can currently be done, but requires 2 config files and runs most of mkosi's pipeline redundantly

[DaanDeMeyer]

@NekkoDroid I sympathize but this would be very painful to implement. Isn't this mostly covered with Incremental=yes and just invoking mkosi twice, each time passing a different format via --format?

[NekkoDroid]

I don't exactly need this anymore, since I somewhat found a better way to handle it.

More specifically the disk output actually installs the kernel, modules and firmware ontop of a more minimal subimage that could in theory be used for containers (results also in the tar being significantly smaller).

So I'd be fine with closing this. Every time I also looked into implementing this I've given up after a bit.