Add pending `SpliceDetails` to `ChannelDetails` #23521

Job	Run time
ext-test	7m 47s
fuzz_sanity	17m 58s
build-nostd / build (self-hosted, 1.75.0)	20m 40s
linting	2m 27s
build-bindings / build (self-hosted, 1.75.0)	29m 13s
build-cfg-flags / build (self-hosted, 1.75.0)	15m 42s
check_release	3m 1s
check_docs	7m 42s
fuzz	1h 31m 1s
rustfmt	32s
tor-connect	7m 8s
build-workspace / build (self-hosted, 1.75.0)	16m 1s
build-features / build (self-hosted, 1.75.0)	38m 25s
build-sync / build (self-hosted, 1.75.0)	8m 16s
benchmark	18m 2s
coverage	53m 21s
notify-failure	0s
	5h 37m 16s

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