Merge branch 'selftests-bonding-use-slowwait-when-waiting'

Hangbin Liu says:

====================
selftests: bonding: use slowwait when waiting

There are a lot waitings in bonding tests use sleep. Let's replace them with
slowwait(added in the first patch). This could save much test time. e.g.

bond-break-lacpdu-tx.sh
  before: 0m16.346s
  after: 0m2.824s

bond_options.sh
  before: 9m25.299s
  after: 6m14.439s

bond-lladdr-target.sh
  before: 0m7.090s
  after: 0m6.148s

In total, we could save about 180 seconds.
====================

Link: https://lore.kernel.org/r/20240205130048.282087-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>