qa/cephadm: zap raw devices before OSD deployment

qa/cephadm: zap raw devices before OSD deployment

ceph_osds() assumes all teuthology scratch devices are clean
and directly usable by:

 > ceph orch apply osd --all-available-devices --method raw

However, in practice some devices may retain stale BlueStore metadata
(or other data) from previous runs. cephadm correctly skips such
devices, leading to fewer OSDs than expected and causing the test to
timeout waiting for an exact OSD count.

This change adds a pre-deployment cleanup step for `raw-osds` that:
- zaps any existing BlueStore metadata (`ceph-bluestore-tool zap-device`)
- removes filesystem signatures (`wipefs --all`)
- clears initial disk data (`dd`)

This ensures all scratch devices are truly available for OSD
deployment and prevents mismatches between expected and actual OSD
counts.

Fixes: https://tracker.ceph.com/issues/75218
Signed-off-by: Redouane Kachach <rkachach@ibm.com>