Attachment hash same content fix

[sazid]

PR Type

Feature + Bug Fix

Overview

• Fix attachments having same content but different file name not working properly
• Attachments having same content will never be downloaded twice (even if they have different names, they are in different test cases or steps, etc.)
• Use the hash as the file name so that the probability of collision is always the same as the probability of collision of the hash coming from server.
• Attachments across different servers with same content will never be downloaded twice.