[3.14] gh-138004: Fix setting a thread name on OpenIndiana (GH-138017) (#138384)

gh-138004: Fix setting a thread name on OpenIndiana (GH-138017)

Encode Solaris/Illumos thread names to ASCII, since
OpenIndiana does not support non-ASCII names.

Add tests for setting non-ASCII name for the main thread.
(cherry picked from commit c19db1d2b8935b6f4f775a0957a076f1864fbf80)

Co-authored-by: jadonduff <jadon_duff@icloud.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>