loader: implement package maps #7562

Job	Run time
Build slim tarball	1m 16s
aarch64-linux: Cache V8 build	23s
x86_64-darwin: with shared libraries	2h 3m 28s
aarch64-darwin: with shared libraries	28m 31s
x86_64-linux: with shared libraries	30m 5s
aarch64-linux: with shared boringssl-0.20260508.0	25m 45s
aarch64-linux: with shared openssl-3.5.6	26m 2s
aarch64-linux: with shared openssl-1.1.1w	26m 19s
aarch64-linux: with shared openssl-3.0.20	26m 35s
aarch64-linux: with shared openssl-3.6.2	26m 0s
aarch64-linux: with shared openssl-4.0.0	27m 14s
	5h 41m 38s

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