[Bug] Fix program storage size definitions.

[laurensvalk]

Describe the bug
Since pybricks/pybricks-micropython@2e97a74 and related commits, there are 4 different places where maximum size is defined/constrained and with different values, when it used to be just 1.

This causes situations where you can run programs that can't be saved, etc.

I'll have a look at how it works since the revision to see if we can make it more consistent.