Move real/integer bounds attributes to properties

[kroenlein]

This PR migrates the lower_bound and upper_bound attributes of IntegerBounds and RealBounds objects to properties, creating getters & setters and locating validation code in those subroutines. It also moves responsibility for verifying that required positional arguments were passed from an explicit default argument check to the compiler.

Technically breaking, since it migrates what was formerly a ValueError to a TypeError and adds setter constraints that were previously bypassed if the user modified objects. Such objects were already considered invalid by Citrine Platform.

This should represent no meaningful change in behavior.

[anoto-moniz]

Only comment is the one about unnecessary ordering, but it only impacts us, it's not a big deal if you wanna ignore it.