Resource-service : Introduce changes to enable multiple replicas

[RealAnna]

As summarised in #6749 , there are a few changes needed to make the resource-service highly available (#6686) :

• Make sure that there is an appropriate retry logic for every part in the service/stage manager in which we write something to the repo to avoid failing for no fast forward updates when multiple replicas try to change a repo. This is for sure missing at least in deleteResource. 1SP

A draft implementation is available in the relative PoC

Technical Details

• Extend the Integration Test matrix with a new entry to run multiple replicas with the new git model

DoD

• Integration tests pass with multiple replicas of resource-service using directory stages running