[POA-2003] Set obfuscation enum in witness method meta

[mudit-postman]

• In this PR, we have added support to identify whether a witness payload is obfuscated or not.
• We are setting the Obfuscation attribute to ZERO_VALUE in the obfuscation() function and NONE in the else branch in the queueUpload() function in backend_collection.go.
  • ZERO_VALUE assignment is still kept to update the value if the witness is obfuscated later in report_buffer.go due to the large size
• Also updated the observability-ir version.

[liujed]

* We are setting `Obfuscation` attribute to `ZERO_VALUE` in `obfuscation()` function. The default enum value is `NONE`

Please see postmanlabs/observability-ir#15 (comment).