Rollup merge of #154132 - bjorn3:fix_missing_feature_gate, r=Mark-Simulacrum

Add missing num_internals feature gate to coretests/benches

This will allow getting rid of the patch at https://github.com/rust-lang/rustc_codegen_cranelift/blob/main/patches/0030-sysroot_tests-Add-missing-feature-gate.patch

Author: jhpratt