try_* variants for slices

[stijnfrishert]

Looking at the interface, I'm missing:

• try_alloc_slice_clone()
• try_alloc_slice_copy()
• try_alloc_slice_fill_clone()
• try_alloc_slice_fill_copy()
• try_alloc_slice_fill_default()
• try_alloc_slice_iter()
• try_alloc_slice_with()

Need try_alloc_slice_fill_copy() and try_alloc_slice_fill_default() myself, though why not add all while we're at it?

Is there a specific reason these weren't added?

[stijnfrishert]

Ah, turns out try_* is for actual OS OOM, not the capacity given to Bump::with_capacity().

In that case I'm ok without these functions, but leaving the issue open for others.