crypto/scheduler: rename slave to worker

crypto/scheduler: rename slave to worker

This patch replaces the usage of the word 'slave' with more
appropriate word 'worker' in QAT PMD and Scheduler PMD
as well as in their docs. Also the test app was modified
to use the new wording.

The Scheduler PMD's public API was modified according to the
previous deprecation notice:
rte_cryptodev_scheduler_slave_attach is now called
rte_cryptodev_scheduler_worker_attach,
rte_cryptodev_scheduler_slave_detach is
rte_cryptodev_scheduler_worker_detach,
rte_cryptodev_scheduler_slaves_get is
rte_cryptodev_scheduler_workers_get.

Also, the configuration value RTE_CRYPTODEV_SCHEDULER_MAX_NB_SLAVES
was renamed to RTE_CRYPTODEV_SCHEDULER_MAX_NB_WORKERS.

Signed-off-by: Adam Dybkowski <adamx.dybkowski@intel.com>
Acked-by: Fan Zhang <roy.fan.zhang@intel.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>