Make Upload related classes more generic

Renames Python classes that refer to Upload to something to FileService.
We added this change because these classes now handle downloading as
well as uploading.

tests/domain/cloud/test_azure_file_service.py

@@ -1,4 +1,4 @@
-from atst.domain.csp.file_uploads import AzureUploader
+from atst.domain.csp.files import AzureFileService
 from azure.storage.blob.models import Blob
 
 
@@ -14,9 +14,9 @@ class MockBlockBlobService(object):
 
 
 def test_download_task_order_success(app, monkeypatch):
-    uploader = AzureUploader(config=app.config)
-    uploader.BlockBlobService = MockBlockBlobService
+    file_service = AzureFileService(config=app.config)
+    file_service.BlockBlobService = MockBlockBlobService
 
-    task_order = uploader.download_task_order("test.pdf")
+    task_order = file_service.download_task_order("test.pdf")
     assert task_order["name"] == "test.pdf"
     assert task_order["content"] == b"mock content"