Add additional labels in exporter metrics

[Jasstkn]

I would like to see the following labels:

• container name
• experiment name
• application namespace

it will help to distinguish results and make a useful report based on it.

[ksatchit]

• May be useful to update this into chaosresult and let exporter pick this. cc: @ispeakc0de @rahulchheda

[ksatchit]

This requirement was revisited in a recent slack discussion: https://kubernetes.slack.com/archives/CNXNB0ZTN/p1614872164161700