Limit the number of active curl handles #2375

Job	Run time
eval	45s
build_x86_64-linux / build	4m 5s
build_aarch64-darwin / build	4m 14s
build_aarch64-linux / build	0s
build_aarch64-linux / manual	0s
build_aarch64-linux / vm_tests_smoke	0s
build_aarch64-linux / success	5s
build_aarch64-linux / flake_regressions	0s
build_aarch64-linux / test	-1s
build_aarch64-linux / vm_tests_all	-1s
build_aarch64-darwin / manual	1m 11s
build_aarch64-darwin / test	4m 0s
build_aarch64-darwin / vm_tests_smoke	0s
build_aarch64-darwin / vm_tests_all	0s
build_aarch64-darwin / flake_regressions	0s
build_aarch64-darwin / success	3s
build_x86_64-linux / vm_tests_smoke	6m 10s
build_x86_64-linux / manual	56s
build_x86_64-linux / test	4m 5s
build_x86_64-linux / flake_regressions	-1s
build_x86_64-linux / vm_tests_all	-1s
build_x86_64-linux / success	4s
success	30s
publish	0s
	26m 4s

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