DeployArtifact does not support upload by checksum

[beiriannydd]

New function DeployArtifactByChecksum (or version bump for DeployArtifact adding checksum *ArtifactChecksums parameter)

• If checksum is not nil (could come from earlier DeployArtifact response or be calculated specifically)
• Try to deploy by checksum (use header to specify checksum as per documentation), do not send file in body.
• If 404 is received, or a checksum was not passed do deploy as normal with file in body.
  This will make it quicker to generate "latest" versions of files or to add files unchanged by a build since the last upload
  Alternatively add DeployArtifact method on CreatedStorageItem which functions as above.
  The former has the advantage that existing artifacts would not require an upload even if they were uploaded by a different process.