(feature) Introduce a jitter on the time to retrieve configuration file

[thomaspoignant]

Context

As of today when we configure the pollingInterval we have a the same configuration on all our services.
It means that if started at the same time, all services will retrieve the configuration exactly at the same time, which can cause huge traffic in a short period of time.

Requirement

We should add an option in GO Feature Flag to allow to use a jitter to add some randomization in the time to retrieve the files.

When this option is set to true, we accept that the retrieval time will not be exactly the one configured, but it will help to avoid having all services calling the storage of your file at the same time.