Add computation time in JSON RAO result metadata

[murgeyseb]

Describe the current behavior

When performing studies and analysis around RAO computation, time performance needs extra outputs for analysing computation time. It could be valuable to have actual RAO computation time available inside RAO result, and especially its JSON output that could be analysed offline for generating reports and indicators about performance.

Describe the expected behavior

RAO result JSON file contains in any form the computation time, and/or perhaps computation start and end timestamps.

Describe the motivation

Making it easier to analyse runs performance afterwards, based only on RAO result JSON output

Extra Information

No response