tracing: lock contention analysis

Currently there is a macro DEBUG_LOCKCONTENTION (see developer-notes.md) to enable logging of contention. The disadvantage of this method is that bitcoind needs to be especially compiled with that enabled, and when enabled this quickly produces huge log files, and has a relatively large overhead.

This PR introduces some tracepoints and adds a tracing script lock_contention_analysis.bt that can be started at any time while bitcoind is running. This has low overhead and gives better analysis possibilities.

When the script is attached with sudo bpftrace contrib/tracing/lock_contention_analysis.bt, you'll get a markdown formatted output that looks like this:

timestamp	Lock	waiting duration	waiting at	blocked by
12:41:05.512089	m_mutex	4491µs	./checkqueue.h ( 175)	./checkqueue.h ( 78)
12:41:05.861322	cs_main	535058µs	net_processing.cpp (1607)	validation.cpp (2994)
12:41:06.655427	m_mutex	4012µs	./checkqueue.h ( 78)	./checkqueue.h ( 78)
12:41:06.675967	cs_main	650117µs	net_processing.cpp (1607)	validation.cpp (2994)
12:41:06.894090	m_mutex	2747µs	./checkqueue.h ( 78)	./checkqueue.h ( 78)
12:41:06.961872	cs_main	142277µs	net_processing.cpp (1607)	validation.cpp (2994)
12:41:07.363535	cs_main	395851µs	net_processing.cpp (1607)	validation.cpp (2994)
12:41:07.583226	cs_main	69281µs	net_processing.cpp (1607)	validation.cpp (2994)
12:41:07.746665	cs_main	157604µs	net_processing.cpp (1607)	validation.cpp (2335)
12:41:07.958787	m_mutex	3041µs	./checkqueue.h ( 175)	./checkqueue.h ( 78)
12:41:07.958801	m_mutex	2970µs	./checkqueue.h ( 78)	./checkqueue.h ( 175)
12:41:07.958842	m_mutex	2956µs	./checkqueue.h ( 78)	./checkqueue.h ( 175)
12:41:07.958853	m_mutex	2898µs	./checkqueue.h ( 78)	./checkqueue.h ( 78)
12:41:07.958862	m_mutex	2820µs	./checkqueue.h ( 78)	./checkqueue.h ( 78)
12:41:07.959201	m_mutex	3028µs	./checkqueue.h ( 78)	./checkqueue.h ( 78)
12:41:07.959218	m_mutex	2916µs	./checkqueue.h ( 78)	./checkqueue.h ( 78)

When monitoring is stopped (press Ctrl+C), the script prints the source locations where it has waited the longest while the script was running (unfortunately there seems to be no way to format this more nicely):

Monitored from 17:12:18.513400 to 17:42:08.565786. top 50 lock contention locations (file, lineNo): µs
[...]
@locked_at_source_line[./net.h, 1233]: 334654
@locked_at_source_line[txmempool.cpp, 823]: 401472
@locked_at_source_line[net_processing.cpp, 4504]: 661670
@locked_at_source_line[net_processing.cpp, 4872]: 668911
@locked_at_source_line[txmempool.cpp, 1096]: 681892
@locked_at_source_line[net_processing.cpp, 4857]: 825963
@locked_at_source_line[net_processing.cpp, 4724]: 826719
@locked_at_source_line[net_processing.cpp, 4677]: 827335
@locked_at_source_line[net_processing.cpp, 4154]: 827972
@locked_at_source_line[net_processing.cpp, 4222]: 828863
@locked_at_source_line[net.cpp, 2329]: 831334
@locked_at_source_line[net_processing.cpp, 4217]: 831451
@locked_at_source_line[net_processing.cpp, 4231]: 839408
@locked_at_source_line[net_processing.cpp, 4198]: 846353
@locked_at_source_line[util/system.cpp, 1035]: 883117
@locked_at_source_line[net.cpp, 1426]: 1398949
@locked_at_source_line[net.cpp, 1422]: 1416004
@locked_at_source_line[net.cpp, 1611]: 1564984
@locked_at_source_line[net_processing.cpp, 4205]: 1668173
@locked_at_source_line[net_processing.cpp, 1334]: 1704239
@locked_at_source_line[validation.cpp, 5173]: 2899013

For this to work I had to add traces to UniqueLock and AnnotatedMixin, and move the implementation into the cpp file (without moving, due to inlining the maximum number of traces of 512 is quickly exhausted)