`std.MultiArrayList`: add `*Bounded` variants and `initCapacity`

Because I accidentially squished two commit and can't figure out how to separate them
again, this also
- standardizes some doc-comments
- makes a slight change to `std.ArrayList`'s `initCapacity`'s doc-comment
86a9a9048eRue04 committed on 1/4/2026, 2:05:34 AMparent0cbaaa5
2 files changedLine totals unavailable