[experiment] Remove PROGRAM_SIZE from type

[mcalancea]

naure:

• Issue #566.
• Start a move towards circuit parameters as values, instead of as type.

[matthiasgoergens]

I agree that we probably went a bit overboard with trying to using usize in types everywhere, even when it's not useful.

[naure]

Before merging, let’s compare this with the approach of cb.platform in https://github.com/scroll-tech/ceno/pull/608

[naure]

Preferring #608.