Be stricter about ways to create UInt64/32

[mitschabaude]

Why: Currently, it's very easy to create UInt64 or UInt32 from a Field without range-checking it, without given any hint that this is unsafe. For Bool we do a much better job: the only way to create it from a Field is with Bool.Unsafe.ofField()

How:

• Remove Field as input type from UInt64.from(). Replace with something like UInt64.Unsafe.fromField()
• Remove Field as possible constructor input. The tricky thing is that UInt64 really consists of 1 Field, so we need a way to construct it from field at least in internal methods. There are two ways around this:
  • make the constructor take a FieldVar instead of a Field, so that creating it from a Field becomes a less visible and more low-level operation. This is how Bool does it.
  • or make the constructor private externally. This makes the breaking change more breaking though.

[barriebyron]

Please advise @mitschabaude can you help identify the required doc updates?

[mitschabaude]

@barriebyron the UInt64 API changed, so this is about fixing type errors that turn up when switching to the latest o1js version in doc examples

[barriebyron]

Can you help me identify the examples that need updating?