In multi DC setup, tablet load balancer might generate multiple migrations of the same tablet_id but only one is actually commited to the `system.tablets` table.
This PR moved abortion of view building tasks from the same start of the migration (`<no tablet transition> -> allow_write_both_read_old`) to the next step (`allow_write_both_read_old -> write_both_read_old`). This way, we'll abort only tasks for which the tablet migration was actually started.
The PR also includes a reproducer test.
Fixesscylladb/scylladb#25912
View building coordinator hasn't been released yet, so no backport is needed.
Closesscylladb/scylladb#26144
* github.com:scylladb/scylladb:
test/test_view_building_coordinator: add reproducer
topology_coordinator: abort view building a bit later in case of tablet migration
4a83b4eef3