Add support for showing the resolved variant and its attributes in `ResolvedComponentResult` This commit adds a `ResolvedNamedVariantResult getVariant()` method on `ResolvedComponentResult`, which gives access to the resolved variant details. In practice, the details are currently limited to:
- the name of the variant - the attributes attached to this variant
The attributes are desugared: if the original variant had strongly-typed attributes, what we get by the result of this call is an attribute container where all attributes are of type `String`. As a consequence, it should only be used for diagnostics.
The `ResolveTestFixture` has been adjusted so that we can now (optionally) check the selected variant and its attributes. One test has been adjusted to check the variant.