CLEANUP: thread: now remove the temporary CPU node binding code

CLEANUP: thread: now remove the temporary CPU node binding code

This is now superseded by the default "safe" cpu-policy, and every time
it's used, that code was bypassed anyway since global.nbthread was set.
We can now safely remove it. Note that for other policies which do not
set a thread count nor further restrict CPUs (such as "none", or even
"safe" when finding a single node), we continue to go through the fallback
code that automatically assigns CPUs to threads and counts them.