chore: Add georeplication variable check on Quay startup

If georeplication is turned on, Quay should check whether the QUAY_DISTRIBUTED_STORAGE_PREFERENCE variable is correctly defined and present during startup.

QE testing acceptance:

Run Quay with FEATURE_STORAGE_REPLICATION: true  in config.yaml file but do not define the QUAY_DISTRIBUTED_STORAGE_PREFERENCE env. variable. Quay should exit during bootstrapping. If FEATURE_STORAGE_REPLICATION: false then Quay should start normally without the env. variable set.