Implement subcommand `benchttp upload`

[GregoryAlbouy]

Description

🚧 WIP

benchttp upload path/to/benchttp.report.20220304090000.json

Tasks

• Create cmdUpload in /cmd
• Decode json file as output.Report
• ⚠️ TODO: determine additional validations to perform
• Send it to server via export.HTTP

Suggestions

Notes

• Not critical if we consider the possibility to upload a report via the webapp.