Replace isc_qsbr with liburcu-qsbr

The qp-trie has been refactored to use call_rcu() for safe memory reclamation.

This change makes cleanup more asynchronous, so it also required some fixes elsewhere:

• The cross-links between managed zones and their loops and timers have been made more accurate
• I have put an rcu_barrier() in isc_mem_destroy() which I hope will ensure asynchronous cleanups are completed before shutdown
• I have added a small call_rcu() wrapper to help thread sanitizer understand it
• The tsan CI jobs have been adjusted to suppress complaints about rcu_barrier() which can't be fixed with a wrapper

When testing a million-zone configuration,

version	peak rss	cpu usage
9.19.11	11387820	120s
main	11644664	157s
this	10936148	120s

Closes #3936 (closed)

Closes #4019 (closed)