http: replace WorkQueue and threads handling for ThreadPool #866

Job	Run time
test each commit	0s
macOS native, no depends, sqlite only, gui	22m 34s
determine runners	3s
Windows native, VS 2022	1h 31m 12s
macOS native, fuzz	11m 53s
Windows native, fuzz, VS 2022	37m 26s
Linux->Windows cross, no tests	56m 32s
lint	2m 2s
ASan + LSan + UBSan + integer, no depends, USDT	1h 29m 4s
32 bit ARM, unit tests, no functional tests	36m 36s
No wallet, libbitcoinkernel	53m 28s
macOS-cross to arm64	48m 48s
previous releases, depends DEBUG	52m 55s
no IPC, i686, DEBUG	1h 19m 37s
MSan, depends	1h 19m 47s
tidy	1h 46m 47s
Alpine (musl), depends, gui	1h 30m 36s
macOS-cross to x86_64	43m 56s
TSan, depends, no gui	1h 1m 54s
fuzzer,address,undefined,integer, no depends	2h 12m 16s
Windows, test cross-built	44m 42s
	19h 2m 8s

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