[storage/resource-manager] Merge the duplicated items referenced by FileShare, BlobContainer Get/List API

For some resources (FileShare, BlobContainer), the [Get API](https://github.com/Azure/azure-rest-api-specs/blob/master/specification/storage/resource-manager/Microsoft.Storage/stable/2019-06-01/file.json#L350) and [List API ](https://github.com/Azure/azure-rest-api-specs/blob/master/specification/storage/resource-manager/Microsoft.Storage/stable/2019-06-01/file.json#L159)return different objects, but their definitions are almost the same.
In a new API version, we should merge them and use one to replace the other one, i.e. we can replace [ListContainerItem ](https://github.com/Azure/azure-rest-api-specs/blob/3f1d9a2fd7d79c0e10cca4a4750a00e725ddc541/specification/storage/resource-manager/Microsoft.Storage/stable/2021-04-01/blob.json#L1226)with [BlobContainer](https://github.com/Azure/azure-rest-api-specs/blob/3f1d9a2fd7d79c0e10cca4a4750a00e725ddc541/specification/storage/resource-manager/Microsoft.Storage/stable/2021-04-01/blob.json#L1000), replace [FileShareItem ](https://github.com/Azure/azure-rest-api-specs/blob/3f1d9a2fd7d79c0e10cca4a4750a00e725ddc541/specification/storage/resource-manager/Microsoft.Storage/stable/2019-06-01/file.json#L581)with [FileShare](https://github.com/Azure/azure-rest-api-specs/blob/3f1d9a2fd7d79c0e10cca4a4750a00e725ddc541/specification/storage/resource-manager/Microsoft.Storage/stable/2019-06-01/file.json#L548).

Anyway，if there are specific reason we need keep them separated, like they will have different properties in the future, please call out.