hexpm: support vulnerability info from Hex #12685

Job	Run time
validate	22s
rustfmt	19s
test-wasm	1m 44s
lint-build	1m 0s
test (stable, x86_64-unknown-linux-musl)	6m 50s
test (stable, x86_64-unknown-linux-gnu)	3m 23s
test (stable, aarch64-unknown-linux-musl)	4m 24s
test (stable, aarch64-apple-darwin, macos-latest, arm64, cargo, true)	6m 8s
test (stable, x86_64-pc-windows-msvc)	5m 23s
test (stable, aarch64-unknown-linux-gnu)	3m 46s
test (stable, x86_64-apple-darwin)	18m 8s
test-projects	2m 42s
	54m 9s

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