Introduce FundingContributionBuilder API #22963

Job	Run time
benchmark	16m 31s
ext-test	7m 36s
tor-connect	7m 23s
fuzz_sanity	8m 38s
linting	2m 28s
check_release	2m 59s
rustfmt	13s
check_docs	8m 0s
fuzz	49m 34s
build-sync / build (self-hosted, 1.75.0)	29m 37s
build-nostd / build (self-hosted, 1.75.0)	13m 39s
build-cfg-flags / build (self-hosted, 1.75.0)	12m 26s
build-features / build (self-hosted, 1.75.0)	35m 59s
build-bindings / build (self-hosted, 1.75.0)	28m 51s
build-workspace / build (self-hosted, 1.75.0)	19m 41s
coverage	21m 29s
notify-failure	-1s
	4h 25m 3s

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