Add the option to co-locate tablets of different tables. For example, a base table and its CDC table, or a local index.
main changes and ideas:
* "table group" - a set of one or more tables that should be co-located. (Example: base table and CDC table). A group consists of one base table and zero or more children tables.
* new column `base_table` in `system.tablets`: when creating a new table, it can be set to point to a base table, which the new table's tablets will be co-located with. when it's set, the tablet map information should be retrieved from the base table map. the child map doesn't contain per-tablet information.
* co-located tables always have the same tablet count and the same tablet replicas. each tablet operation - migration, resize, repair - is applied on all tablets in a synchronized manner by the topology coordinator.
* resize decision for a group is made by combining the per-table hints and comparing the average tablet size (over all tablets in the group) with the target tablet size.
* the tablets load balancer works with the base table as a representative of the group. it represents a single migration unit with some `group_size` that is taken into account.
* view tablets are co-located with base tablets when the partition keys match.
Fixes https://github.com/scylladb/scylladb/issues/17043
backport is not needed. this is preliminary work for support of MVs and CDC with tablets.
Closesscylladb/scylladb#22906
* github.com:scylladb/scylladb:
tablets: validate no clustering row mutations on co-located tables
raft_group0_client: extend validate_change to mixed_change type
docs: topology-over-raft: document co-located tables
tablet-mon.py: visual indication for co-located tablets
tablet-mon.py: handle co-located tablets
test/boost/view_schema_test.cc: fix race in wait_until_built
boost/tablets_test: test load balancing and resize of co-located tablets
test/tablets: test tablets colocation
tablets: co-locate view tablets with base when the partition keys match
test/pylib/tablets: common get_tablet_count api
test_mv_tablets: use get_tablet_replicas from common tablets api
test/pylib/tablets: fix test api to read tablet replicas from base table
tablets: allocator: create co-located tables in a single operation
alternator: prepare all new tables in a single announcement
migration_manager: add notification for creating multiple tables
tablets: read_tablet_transition_stage: read from base table
storage service: allow repair request only on base tables
tablets: keyspace_rf_change: apply on base table
storage service: generate tablet migration updates on base tables
tablets: replace all_tables method
tablets: split when all co-located tablets are ready
tablets: load balancer: sizing plan for table groups
tablets: load balancer: handle co-located tablets
tablets: allocate co-located tablets
tablets: handle migration of co-located tablets
storage service: add repair colocated tablets rpc
tablets: save and read tablet metadata of co-located tables
tablets: represent co-located tables in tablet metadata
tablets: add base_table column to system.tablets
docs: update system.tablets schema
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