Simplify Creation of parameter declarations

[Chris-Hibbert]

@dtribble suggested this simplification from #3448 while it was under review.

Description

These helper functions reduce the call to declare a governed parameter from

const governedParameterInitialValues = [
  {
    name: MALLEABLE_NUMBER,
    value: 602214090000000000000000n,
    type: ParamType.NAT,
  },
];

to

const governedParameterInitialValues = [
  makeGovernedNat('MalleableNumber', 602214090000000000000000n),
];

which is a pretty substantial reduction for the first thing that a contract author has to do to add governed parameters.

Security Considerations

Nothing substantial. This doesn't change the API for controlling parameters, and it reduces complexity for readers.

Documentation Considerations

We need more thorough documentation for how contract developers can add governance, but this PR simplifies the task to be explained.

Testing Considerations

None.

[dckc]

This makeGovernedNat style seems like it could address some of the dynamic typing woes. Here's hoping...

[dckc]

a small forward step...

[dckc]

ah. not tackling as much as I hoped. But still, forward progress...