[Storage] Azure.Storage.Files.DataLake download APIs are in feature parity with Azure.Storage.Blobs

[nickliu-msft]

Resolves #45418

[nickliu-msft]

A few things of note:

1. Should I add new tests for this change? I'm asking cus
   a. I didn't see any tests for the original Read() and ReadAsync()
   b. Since DataLake lives ontop of Blobs, the "actual processing" methods being called are DownloadStreaming() and
   DownloadContent() which have tests already
2. I did not add ReadTo() and ReadToAsync() since they seem to be already present within DataLake

Let me know thoughts and if I should incorporate anything. Thanks

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

Azure.Storage.Files.DataLake

[amnguye]

A few things of note:

1. Should I add new tests for this change? I'm asking cus
   a. I didn't see any tests for the original Read() and ReadAsync()

The tests are here:
https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/storage/Azure.Storage.Files.DataLake/tests/FileClientTests.cs#L3426

b. Since DataLake lives ontop of Blobs, the "actual processing" methods being called are DownloadStreaming() and
DownloadContent() which have tests already

That being true, I would still like the E2E tests, as that follows the current testing standard we do for when we add any new API.

[seanmcc-msft]

@tg-msft and @schaabs, this PR involves some public interface changes, can you take a look?

[jaschrep-msft]

Comments on organization and presentation.

[jaschrep-msft]

Since DataLake lives ontop of Blobs, the "actual processing" methods being called are DownloadStreaming() and
DownloadContent() which have tests already

@nickliu-msft yes, but we are not just testing that the blobs download works correctly, we are testing that our arguments are mapped onto it correctly and our results are properly translated. Ideally, we would have mocking foundation in place to more directly test that, but for now recordings will have to do. (Also though it's good to have some full end to end tests as well so we'd still have some of these even if we were able to go with a mocking route.)