Prior to this change, the version fields for DSC used an arbitrary
`String` for both resources and extensions. The generated schema for
those types then reports that any string is valid and DSC must check
every time it needs to process the version for whether the version is
semantic or an arbitrary string.

This change follows the Rust "parse, don't validate pattern" by defining
a `TypeVersion` enum with the `Semantic` and `String` variants. If the
version can be parsed as a semantic version, the type creates it as
an instance of `TypeVersion::Semantic` and otherwise creates it as
`TypeVersion::String`.

The `TypeVersion` enum implements several conversion and comparison
traits to make using the newtype more ergonomic. It also defines helper
methods `is_semver()` and `matches_semver_req()` for easier usage.

When comparing an instance of `TypeVersion`:

- A semantic version is always greater than an arbitrary string version.
  This applies both when comparing `TypeVersion::String` instances to
  `TypeVersion::Semantic` and to `semver::Version`.
- Arbitrary string version comparisons are case-insensitive. `Foo` and
  `foo` are equal but `Foo` is greater than `Bar`.
- You can directly compare instances of `TypeVersion` to string slices,
  `String` instances, and `semver::Version` instances in addition to
  other instances of `TypeVersion`.
- The trait implementations support using `==`, `>`, and `<` operators
  for easier reading.

The newtype overhauls the JSON Schema for versions to help users get
better validation and IntelliSense when authoring manifests.

Finally, this change adds comprehensive integration tests for the
newtype and its implementations as well as documentation for the type
and its public methods.