arm64: debug: add a migration test for watchpoint state

Test the migration of watchpoint state. Program as many watchpoints as
possible, migrate, and check that we get the corresponding exceptions.

Signed-off-by: Ricardo Koller <ricarkol@google.com>
Message-Id: <20211210165804.1623253-3-ricarkol@google.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>