Allow cancellation of pending splice funding negotiations #23202

Job	Run time
fuzz_sanity	17m 27s
check_release	2m 57s
check_docs	7m 21s
ext-test	7m 14s
linting	2m 40s
rustfmt	15s
build-nostd / build (self-hosted, 1.75.0)	22m 24s
fuzz	1h 5m 14s
build-bindings / build (self-hosted, 1.75.0)	30m 29s
tor-connect	7m 23s
benchmark	15m 7s
build-workspace / build (self-hosted, 1.75.0)	15m 40s
build-features / build (self-hosted, 1.75.0)	34m 49s
build-cfg-flags / build (self-hosted, 1.75.0)	17m 12s
build-sync / build (self-hosted, 1.75.0)	26m 42s
coverage	22m 32s
notify-failure	0s
	4h 55m 26s

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