remove `isLegacyGetEnabled` flag from `Data` and `Cache` service

Related to #531 and #550. At some point after #550, we will need to remove this flag entirely, dropping support for the legacy shape.

> This should be a major release of hyper core

```
As a hyper developer
I would like hyper data service and hyper cache service "get" apis to return a hyper response shape
So that consumers will receive the hyper response shape across all hyper service apis
```

## Scenarios

Only allow hyper response shape
```
GIVEN I am a developer
WHEN I am calling the Data Service "get document" or Cache Service "get value" api
THEN I will receive the hyper response shape
```