CLEANUP: task: split the large tasklet_wakeup_on() function in two

CLEANUP: task: split the large tasklet_wakeup_on() function in two

This function has become large with the multi-queue scheduler. We need
to keep the fast path and the debugging parts inlined, but the rest now
moves to task.c just like was done for task_wakeup(). This has reduced
the code size by 6kB due to less inlining of large parts that are always
context-dependent, and as a side effect, has increased the overall
performance by 1%.