Canonicalize registry resource schema

[michaeltlombardi]

PR Summary

This change prototypes shifting from separately maintained schemas in the schemas folder to deriving fully expressed schemas from the Rust structs in the code. This change shows how we can begin to:

1. Define full, enhanced JSON schemas for data types in Rust and export those schemas in both canonical and enhanced variants.
2. Migrate from in-code strings to referencing data keys, making it easier to change documentation and messages without editing the code and preparing the projects for internationalization and localization.
3. Define reusable helpers for the projects to minimize rework.

PR Context

Deriving more descriptive schemas from the structs required using the alpha release of schemars v1, which added support for more easily defining schemas using attributes and supports deriving schemas adhering to the JSON Schema 2020-12 specification.

Of particular note are the following changes to the JSON Schema for instances of the registry resource:

• Use JSON Schema specification draft 2020-12 instead of draft 07.
• Added title and description for every property as documentation.
• Added a regular expression check for keyPath to ensure it starts with a valid hive identifier.
• Added the $id keyword to ensure that users and integrating developers can get a copy of the schema online instead of always calling the command.
• Marked the keyPath property as required.
• Marked the valueName property as required only when valueData is specified.
• Marked the _metadata property and its whatIf sub-property as read-only.
• Defined the default value for the _exist property as true.

In the process of implementing this prototype, this change also addressed a few related challenges:

• In order to define longer strings for documentation keywords in the schemas, this change uses the rust_i18n library to provide a way to map complex or lengthy strings to key names. This also prepares the project for internationalization and localization, though the change only defines translations for English.

• To minimize rework, the struct attributes define the JSON Schema with VS Code's annotation keywords, which enhance the authoring and editing experience in VS Code, but are generally ignored by other tools and libraries. To account for the difference between the canonical (stictly 2020-12 compatible) schema and the enhanced schema this change also:

  1. Adds the --enhanced option to the registry schema command to enable returning the enhanced schema, but default to returning the canonical schema as is current behavior.
  2. Defines the remove_vscode_keywords function to recursively remove those keywords. While the function is implemented in the registry resource in this prototyping PR, it better belongs in dsc_lib.
  3. Defines the get_schema_generator function to return a generator with the correct settings for canonical and enhanced schemas. In both cases, it no longer adds the null type for optional items in the struct to better conform with JSON Schema. In JSON Schema, specifying null for a property value is not semantically the same as not specifying the property. For the enhanced schemas, it also uses definitions instead of $defs, as VS Code doesn't understand retrieving references from $defs.

The scope of these changes is limited to the registry project only.