pthread_exit seems to have been adopted as some trend in the early days of glibc 2.2.5 based on https://bugs.mysql.com/bug.php?id=82886 and the dates of initial pthread_exit call inclusions.

These seem to have been copied without much consideration.

This task takes a bit of debt back and just leaves our threads to exit, with the args that where being provided to pthread_exit,

This backports the removal and cleanup performed in the 11.4 merge - 2719cc4925c032f483edb0e61c0f487e0c429ae6