[Feature Request] search traces by querying on span duration

[ashishagg]

We should allow to search traces based on span duration.
For. e.g say we want to look few sample traces where the spans from Service 'A' have duration more than 500ms. Such range queries on span duration should be allowed for better diagnostics.

[ashishagg]

Part of this feature has been completed in this PR
ExpediaDotCom/haystack-traces#205

The remaining work is left on UI, that we will be targeting soon.

[shreyaa-sharma]

Done for backend. Tagging @bulicekj to confirm if UI changes went through.