tests/scaling_up: cover fast node addition for tiered_v2

Parametrize test_fast_node_addition by storage mode. The tiered_v2
flavor creates the topic with redpanda.storage.mode=tiered plus
impl=tiered_v2 and verifies the same fast-movement property: a newly
added node ends up with less than 35% of the average per-node data
footprint, and all data stays readable (prefix served from L1).

Signed-off-by: Evgeny Lazin <4lazin@gmail.com>