Merge bitcoin/bitcoin#30659: wallet: fix UnloadWallet thread safety a… #507

Job	Run time
macOS 13 native, x86_64, no depends, sqlite only, gui	58m 5s
Win64 native, VS 2022	56m 25s
ASan + LSan + UBSan + integer, no depends, USDT	1h 11m 14s
test each commit	0s
	3h 5m 44s

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