net: fix BlockList.fromJSON for IPv4-mapped IPv6 rules #8422

Job	Run time
Build slim tarball	1m 22s
aarch64-darwin: with shared libraries	2h 2m 43s
x86_64-linux: with shared libraries	2h 2m 30s
x86_64-darwin: with shared libraries	3h 44m 18s
aarch64-linux: Cache V8 build	25s
aarch64-linux: with shared openssl-3.0.21	23m 30s
aarch64-linux: with shared openssl-3.5.7	23m 47s
aarch64-linux: with shared openssl-3.6.2	23m 25s
aarch64-linux: with shared openssl-4.0.1	23m 14s
aarch64-linux: with shared boringssl-0.20260526.0	23m 14s
aarch64-linux: with shared openssl-1.1.1w	22m 41s
	10h 11m 9s

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