Auto merge of #84082 - andjo403:stabilize_nonzero_leading_trailing_zeros, r=m-ou-se

Stabilize nonzero_leading_trailing_zeros

Stabilizing nonzero_leading_trailing_zeros and due to this also stabilizing the intrinsic cttz_nonzero

FCP finished here: https://github.com/rust-lang/rust/issues/79143#issuecomment-817216153
`@rustbot` modify labels: +T-libs

Closes #79143

diff --cc library/core/src/lib.rs
Simple merge

diff --cc library/core/tests/lib.rs
Simple merge