Create constraint macros that are more ergonomic and concise

[popematt]

As a library TODO (if/when we finish the versioning-via-generics refactoring), we should look at making constraint macros that coalesce failure modes and elide all of the .into()s that are currently required at the call site, turning this:

valid_values(
  vec![
    2.into(), 
    ion_rs::Decimal::new(35, -1).into(),
    5e7.into(),
    "hello".to_owned().into(),
    Symbol::from("hi").into(), 
    NumberRange::new_inclusive(2.into(), 3.into()).unwrap().into()
  ]
)

into something more like:

valid_values! [
  2,
  Decimal::new(35, -1), 
  5e7,
  "hello",
  Symbol::from("hi")
  inclusive_number_range! [2, 3]
],

Originally posted by @zslayton in #190 (comment)