Enable getting adapted resource schema

[SteveL-MSFT]

PR Summary

Enable retrieving schema from an adapted resource.

For an adapted resource manifest based resource, it's retrieved from the manifest which must be embedded.
For a non-manifest adapted resource, the adapter is called with the schema command and passed the resourceType and the adapter needs to return a JSONLine that represents the schema.

Made process_set_delete_args() private since it's only used within the same file

PR Context

Fix #1352
Fix #872

[Copilot]

Pull request overview

This PR enables retrieving schemas from adapted resources. For manifest-based adapted resources, the schema is retrieved from the embedded manifest. For non-manifest adapted resources, the adapter is invoked with the schema command, passing the resource type, and returns the schema as JSON.

Changes:

• Added Schema operation to adapter operations
• Modified schema retrieval to support adapted resources via adapter invocation
• Updated test cases to verify adapted resource schema retrieval

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tools/dsctest/src/args.rs	Added Schema variant to AdapterOperation enum
tools/dsctest/src/adapter.rs	Implemented schema retrieval logic for adapted test resources
tools/dsctest/dsctest.dsc.manifests.json	Updated manifest schemas and added schema command configuration
lib/dsc-lib/src/dscresources/resource_manifest.rs	Introduced SchemaArgKind enum and updated SchemaCommand to use it
lib/dsc-lib/src/dscresources/dscresource.rs	Added adapter-based schema invocation and updated schema retrieval logic
lib/dsc-lib/src/dscresources/command_resource.rs	Added process_schema_args function and updated all functions to pass target_resource
dsc/tests/dsc_resource_schema.tests.ps1	Added test cases for adapted resource schema retrieval
dsc/tests/dsc_adapter.tests.ps1	Updated test expectation to reflect schema structure change

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