Set only the internal name.
Fixes#17036 for both `bitcoind` and `bitcoin-qt`.
Github-Pull: #17038
Rebased-From: 07e4bdba3bd46c3a15dedb0a2660453c300643dc
Tree-SHA512: ed6f1b95a23c4c7863982ee6972429be5af0702ea93f0f17d32d2ef4b01446b1c0528eeadc45289609eda5c02ea68b3d722b8ecdfdf4fff4b02592c2188cc0a0
This work is prerequisite to attaching thread names to log lines and deadlock
debug utilities. This code allows setting of an "internal" threadname per
thread on platforms where thread_local is available.
This commit also moves RenameThread() out of a more general module and adds a
numeric suffix to disambiguate between threads with the same name. It
explicitly names a few main threads using the new util::ThreadRename().
