help with pthread_t deprecation / api changes

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

hi folks,

i'd like to continue work moving to our platform abstracted rte_thread
but ran into a hiccup. for some recent and not so recent apis it appears
they managed to slip in without ever being __experimental. 

as a function of the dpdk project api/abi policy this means we can't
change or remove some of these functions without following the
deprecation process.

the apis that are causing me immediate difficulty are
rte_thread_setname and rte_ctrl_thread_create.

i think the least painful path forward to deprecating and removing these
apis is probably just to introduce the replacements with new names.

1. introduce functions with the following names marked as
   __experimental.

   rte_control_thread_create(rte_thread_t *, ...)
   rte_thread_set_name(rte_thread_t, ...)
   rte_thread_get_name(rte_thread_t, ...)

   along with the new functions, new unit tests will be included.

2. update dpdk internal implementation to use the new functions.

3. immediately remove the following functions from the public headers
   and issue an api deprecation notice for the functions not marked
   experimental.

   rte_ctrl_thread_create(pthread_t *, ...)
   rte_thread_setname(pthread_t *, ...)

4. when the new functions have their __experimental marking removed
   issue an abi deprecation notice for the functions from (2).

i'm open to feedback/suggestions of a better approach if anyone has one
to offer.

thanks!