Simplify storage model of KeyValueBlobTransientStore

KeyValueBlobTransientStore has to store the list of parameters being stored for a given key because it needs to iterate over them. This is currently stored in a JSON structure in a entryKey.paraminfo key but this a problem because:

• we need to do JSON parsing/serialization to change this key
• we need additional locking
• for large number of parameters (which is the case for big batch uploads, in AbstractBatchHandler) and for key/value stores with size limitations, we may go beyond the allowed storage size for a string.

Since NXP-26183, KeyValueStoreProvider.keyStream(prefix) gives us a way to iterate over keys with a given prefix, and this could be used to do a better implementation of the parameters storage.