DNS spec contains two methods that perform the same action and has same description.

In the 2018-03-01-preview swagger has `RecordSets_ListAllByDnsZone` oprationId and `RecordSets_ListByDnsZone` operationId.
Both has 4 parameters:
- resourceGroupName
- zoneName
- $top
- $recordsetnamesuffix

And both has the same description in swagger:
`Lists all record sets in a DNS zone. ` (for RecordSets_ListByDnsZone)
`Lists all record sets in a DNS zone.` (for RecordSets_ListAllByDnsZone)

according to owner team explanation:
`
Both the APIs are exactly the same. The reason for two of them is that for historical reasons, we had exposed the endpoint with /all and it seemed to have some usage in some internal clients. Hence, we had to expose that method publicly and this was signed off by the ARM team. From a developer point of view, both calls are exactly the same and accomplish the same thing.
`

Please add some explanation to the description field so that autogenerated SDK users will not be confused.

Find the 2018-03-01-preview swagger definition containing the RecordSets_ListAllByDnsZone and RecordSets_ListByDnsZone operationIds. Read both descriptions and the surrounding DNS specification, then clarify that the two operations perform the same action and exist for historical compatibility. Done when the generated SDK-facing descriptions distinguish the duplicate methods and the specification remains valid.

Written by the indexing model from the issue text.