Speed up cold cache urllib3/boto3/botocore with batched prefetching #4500

Job	Run time
cargo fmt	27s
cargo clippy (ubuntu-latest)	41s
cargo clippy (windows-latest)	4m 1s
build binary \| macos aarch64	1m 17s
build binary \| linux	1m 42s
build binary \| macos x86_64	1m 30s
build binary \| windows	4m 35s
cargo test \| ubuntu	3m 16s
check windows trampoline	3m 15s
cargo test \| windows	8m 55s
cargo test \| macos	3m 25s
check system \| python on macos aarch64	11s
check cache \| macos aarch64	13s
check system \| homebrew python on macos aarch64	14s
check system \| python on macos x86_64	46s
check system \| python on debian	51s
check system \| python on centos	32s
check system \| alpine	15s
check cache \| ubuntu	49s
check system \| python on fedora	27s
check system \| pypy on ubuntu	23s
check system \| pyston	3m 50s
check system \| python on ubuntu	11s
check system \| amazonlinux	22s
check system \| python via pyenv	1m 49s
check system \| python3.12 via chocolatey	1m 35s
check system \| python3.13 on windows	1m 32s
check system \| conda3.8 on linux	40s
check system \| python3.10 on windows	39s
check system \| python3.10 on windows x86	52s
check system \| conda3.11 on linux	35s
check system \| conda3.8 on windows	2m 20s
check system \| conda3.11 on windows	2m 22s
check system \| conda3.8 on macos	38s
check system \| conda3.11 on macos	37s
	55m 47s

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