dns: return `localhost` IP directly #6808

Job	Run time
Build slim tarball	1m 30s
x86_64-darwin: with shared libraries	43m 45s
aarch64-darwin: with shared libraries	25m 35s
aarch64-linux: Cache V8 build	20s
x86_64-linux: with shared libraries	29m 27s
aarch64-linux: with shared openssl-3.0.19	24m 47s
aarch64-linux: with shared openssl-1.1.1w	24m 27s
aarch64-linux: with shared openssl-3.6.1	23m 53s
aarch64-linux: with shared openssl-4.0.0	24m 13s
aarch64-linux: with shared boringssl-0.20260413.0	24m 27s
aarch64-linux: with shared openssl-3.5.5	24m 31s
	4h 6m 55s

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