Support --force with cph create

[Callek]

Checklist

• I added a descriptive title
• I searched open requests and couldn't find a duplicate

What is the idea?

When modifying a given file that is already in a package, running cph create doesn't seem to re-add or modify files that were already present.

Having a --force that behaves like transmute --force would be useful.

Why is this needed?

In manual testing I:

• extracted a windows package (.tar.bz2) with cph extract
• locally codesigned a binary
• tried to update the .tar.bz2 with cph create ... into the same location as the original

The md5sum of the package did not change, indicating that it was not modified.

What should happen?

The package should be able to be updated/recreated in-place

Additional Context

I created a branch in https://github.com/Callek/conda-package-handling/tree/add-force-create to try and explore doing this, but I ran into an issue with my testing method (it seems the files get updated timestamps) and ran against my wall-clock allotment on looking into this.

I don't know if I'll get back to it, but I'm more than happy if anyone wants to take my work and drive it forward.