config validate command needs to check for duplicate resource names in configuration document

Summary of the new feature / enhancement

In order to avoid errors at runtime, the dsc config validate should detect and provide appropriate error response when a resource name is duplicated in a configuration document.

Configuration:

{
"$schema": "https://aka.ms/dsc/schemas/v3/bundled/config/document.json",
"resources": [
{
"type": "Microsoft.Windows/Registry",
"name": "EnsureTest1Value",
"properties": {
"keyPath": "HKEY_LOCAL_MACHINE\SOFTWARE\TEST",
"valueName": "Test1",
"valueData": { "DWord": 1 },
"_exist": true
}
},
{
"type": "Microsoft.Windows/Registry",
"name": "EnsureTest2Value",
"properties": {
"keyPath": "HKEY_LOCAL_MACHINE\SOFTWARE\TEST",
"valueName": "Test2",
"valueData": { "String": "Hello World!" },
"_exist": true
}
},
{
"type": "Microsoft.Windows/Registry",
"name": "EnsureTest1Value",
"properties": {
"keyPath": "HKEY_LOCAL_MACHINE\SOFTWARE\TEST",
"valueName": "Test",
"valueData": { "String": "Hello World!" },
"_exist": false
}
}
]
}

This below should return false with a reason as duplicate resource name

dsc config validate --file C:\dsc\Demo1.json
valid: true
reason: null

Proposed technical implementation details (optional)

No response

Start with the dsc config validate command and reproduce the configuration example from this issue. Verify that duplicate resource names produce valid: false with a reason identifying the duplicate, rather than valid: true and reason: null.