this series disables operator<<:s for vector and unordered_map, and drop operator<< for mutation, because we don't have to keep it to work with these operator:s anymore. this change is a follow up of https://github.com/scylladb/seastar/issues/1544
this change is a cleanup. so no need to backport
Closesscylladb/scylladb#18866
* github.com:scylladb/scylladb:
mutation,db: drop operator<< for mutation and seed_provider_type&
build: disable operator<< for vector and unordered_map
db/heat_load_balance: include used header
test: define a more generic boost_test_print_type
test/boost: define fmt::formatter for service_level_controller_test.cc
test/boost: include test/lib/test_utils.hh
56d523b071