fs: allocate FSReqPromise stat arrays lazily #8407

Job	Run time
Build slim tarball	1m 13s
aarch64-linux: Cache V8 build	22s
x86_64-darwin: with shared libraries	37m 20s
x86_64-linux: with shared libraries	27m 33s
aarch64-darwin: with shared libraries	25m 33s
aarch64-linux: with shared openssl-4.0.1	23m 13s
aarch64-linux: with shared openssl-3.6.2	24m 6s
aarch64-linux: with shared openssl-3.0.21	24m 18s
aarch64-linux: with shared openssl-3.5.7	24m 3s
aarch64-linux: with shared boringssl-0.20260526.0	24m 3s
aarch64-linux: with shared openssl-1.1.1w	52s
	3h 32m 36s

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