Remove internal data structure duplications to simplify the process of adding new field to the semconv registry.

[lquerel]

The current process of adding a new Semantic Convention Field is as follow.

Let's assume that you want to add the field display_name to the semantic convention groups. It's an optional field
containing a string that represents the display name of the group.

1. Update the weaver_semconv crate to define the new field in src/group.rs. The
   data types defined in weaver_semconv are used to parse the registry YAML files. The following are some guidelines:
   • Optional field should be defined as Option<T>. So display_name should be defined as Option<String>.
   • N-ary fields should be defined as Vec<T>.
   • Other data types are also supported, such as bool, u64, f64, enum, HashMap, etc. The only constraint is
     that the type should implement the serde::Deserialize and serde::Serialize traits.
2. Update the test data accordingly in weaver_semconv/data.
3. Update all the unit tests to cover the new field. The easiest way to do this is to run the following command:
   • cargo test --package weaver_semconv
   • This command will run all the unit tests in the weaver_semconv crate.
   • The tests that fail will be the ones that need to be updated and usually the error message will guide you on what
     needs to be updated (most of the time it's the addition of the new field in some struct or enum initialization).
4. Update the weaver_resolved_schema crate to add the corresponding new field in the "resolved" view of the registry.
   This crate define the data types used to represent the resolved view of the registry.
   • Add the new field in weaver_resolved_schema/src/registry.rs.
5. Update the weaver_resolver crate to define the mapping between the "non-resolved" and "resolved" views of the
   registry.
   • Define the mapping in weaver_resolver/src/registry.rs.
   • Run the unit tests to test your changes: cargo test --package weaver_resolver.
6. Update the weaver_forge crate to generate the new field in data structures used by the template engine.
   • Add the new field in weaver_forge/src/registry.rs.
   • Run the unit tests to test your changes: cargo test --package weaver_forge.
7. Update your templates to use the new field and use the weaver registry generate command to generate and test the
   new templates.

Steps 4 and 6 could be merged as step 6 doesn't really bring any new value in this context.