Simplify passing of SINK config properties to OffsetBackingStore

Implement the same idea used for passing SINK config properties to DatabaseHistory.

For the DatabaseHistory the SINK config properties are passed in DebeziumServer:

configToProperties(config, props, PROP_SINK_PREFIX + name + ".", DatabaseHistory.CONFIGURATION_FIELD_PREFIX_STRING + name + ".", false);

It can be done the same for the OffsetBackingStore:

configToProperties(config, props, PROP_SINK_PREFIX + name + ".", "offset.storage." + name + ".", false);