Add duplicate properties to Validation Report

## 🚀 Feature Proposal

The [validation report](https://github.com/elastic/elastic-client-generator/blob/master/output/schema/validation-errors.json) should contain the information of duplicate properties within a Request. E.g. `query_parameters` has a property `force` and so does `body` in [StopDatafeedRequest](https://github.com/elastic/elastic-client-generator/blob/master/specification/specs/x_pack/machine_learning/stop_datafeed/StopDatafeedRequest.ts#L25).

## Motivation

Feedback loop with the server team to remove this duplicate parameters.

## Example

```
"duplicateProperties": {
"StopDatafeedRequest": {
"force": ["query_parameters", "body"]
}
}
```

Read output/schema/validation-errors.json and the StopDatafeedRequest.ts example first, then trace the validation-report generation entry point. Done means the report records each duplicate property by request, property name, and locations such as query_parameters and body.

Written by the indexing model from the issue text.