Factor out source.dump/source.drop (#4207) #11751

Job	Run time
build_details	3s
build_js	2m 0s
build_opam (4.14.x)	9m 11s
build_opam (5.2.x)	5m 24s
lezer_parse	52s
build_win32 (x64)	15m 21s
build_no_depopts	6m 20s
build_posix (debian_trixie, amd64)	14m 59s
run_tests (@citest)	11m 23s
build_posix (debian_bookworm, amd64)	15m 6s
run_tests (@doctest)	7m 59s
tree_sitter_parse	47s
update_doc	11m 12s
build_posix (ubuntu_oracular, amd64)	15m 21s
run_tests (@mediatest)	12m 37s
build_posix (ubuntu_noble, amd64)	14m 51s
build_posix (alpine, amd64)	11m 56s
fetch_s3_artifacts	1s
build_docker_alpine	1s
build_docker	1s
update_release	1s
build_docker_alpine_minimal	1s
build_docker_minimal	1s
build_docker_release	1s
build_docker_release-minimal	1s
	2h 35m 30s

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