library: upgrade to hashbrown v0.16.1

[cuviper]

This is another step toward unspecializing Copy.

See also #135634 and rust-lang/hashbrown#662

r? @Amanieu
cc @joboet

[rustbot]

The list of allowed third-party dependencies may have been modified! You must ensure that any new dependencies have compatible licenses before merging.

cc @davidtwco, @wesleywiser

These commits modify the library/Cargo.lock file. Unintentional changes to library/Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

[cuviper]

Side note: I would also like to upgrade the hashbrown dependency of the compiler, along with indexmap v2.12.1 using its new bucket API, but we can't do that until TrivialClone is in stage0 (beta).

[cuviper]

Oh, it's more tangled than I realized, because the compiler's hashbrown/nightly still needs to compile in later stages as well. So we can't fully remove the Copy specialization until TrivialClone is in stage0 and we upgrade them all.

So I'll drop that commit here.