Proper way to access dataSet from DataBuilderContext

As of now there are two methods by which we can get dataset from `DataBuilderContext`
- `getDataSet()` (marked as `@Deprecated`)
- `getDataSet(DataBuilder builder)`

While implementing `DataBuilder#process(DataBuilderContext context)` we would need to get dataset and isn't using `context.getDataSet()` is the correct way to access? (If yes then why is it marked as deprecated?)
I don't see a clean way to use `getDataSet(DataBuilder builder)` inside `process`, if I do `getDataSet(this)` there will a NPE as there won't be any `dataBuilderMeta` set with current instance

`getDataSet(DataBuilder builder)` enforces to use only data classes mentioned in `consumes`, `optional` and `access` anyways this enforcement is already happening from executors when calling `process`.
Ref:
- [OptimizedMultiThreadedDataFlowExecutor.java#L251 ](https://github.com/flipkart-incubator/databuilderframework/blob/master/src/main/java/com/flipkart/databuilderframework/engine/OptimizedMultiThreadedDataFlowExecutor.java#L251)
- [SimpleDataFlowExecutor.java#L76](https://github.com/flipkart-incubator/databuilderframework/blob/master/src/main/java/com/flipkart/databuilderframework/engine/SimpleDataFlowExecutor.java#L76)
- [MultiThreadedDataFlowExecutor.java#L232](https://github.com/flipkart-incubator/databuilderframework/blob/master/src/main/java/com/flipkart/databuilderframework/engine/MultiThreadedDataFlowExecutor.java#L232)

Either we have to set `dataBuilderMeta` when processed in `withDataBuilder` [here](https://github.com/flipkart-incubator/databuilderframework/blob/master/src/main/java/com/flipkart/databuilderframework/engine/DataFlowBuilder.java#L178) something like `dataBuilder.setDataBuilderMeta(dataBuilderMeta)` which set's it to dataBuilder instance and can be accessed when processing or make other non-deprecated or I should be missing something 😅

Start with DataBuilderContext and DataFlowBuilder around withDataBuilder, then compare how SimpleDataFlowExecutor, MultiThreadedDataFlowExecutor, and OptimizedMultiThreadedDataFlowExecutor invoke process. Trace when dataBuilderMeta is available and how each dataset-access method is intended to work. Done means the process API has one clear, non-deprecated dataset access path without the reported null-pointer risk.

Written by the indexing model from the issue text.