repair: Introduce partition_key_and_mutation_fragments
repair: Introduce partition_key_and_mutation_fragments

Represent a partition_key and frozen_mutation_fragments within the
partition_key.

scylladb/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla