RFC for PoC of bolt12 contacts formally known as a BLIP 42 #21032

Job	Run time
check_release	2m 59s
ext-test	5m 33s
check_docs	5m 10s
build (macos-latest, stable)	4m 40s
benchmark	1m 38s
build (self-hosted, 1.75.0)	1m 47s
build (self-hosted, stable)	3m 48s
build (macos-latest, 1.75.0)	1m 35s
build-tx-sync (macos-latest, beta)	4m 42s
build (windows-latest, stable)	7m 40s
build-tx-sync (macos-latest, stable)	6m 8s
build-tx-sync (macos-latest, 1.75.0)	1m 8s
fuzz	4m 42s
build (self-hosted, beta)	5m 49s
rustfmt	15s
build-tx-sync (ubuntu-latest, beta)	4m 40s
build-tx-sync (ubuntu-latest, stable)	4m 57s
linting	1m 4s
build-tx-sync (ubuntu-latest, 1.75.0)	41s
coverage	0s
	1h 8m 56s

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