fix: use ipairs in functional.all and add basic test coverage

[DavidAtBede]

fix(functional): use ipairs in all to avoid incorrect iteration over tables

Previously, functional.all used pairs, which can iterate non-numeric keys
and lead to incorrect behavior when passed list-style tables.

This patch switches to ipairs, preserving the existing (k, v) arity of the
predicate function but ensuring predictable, index-ordered traversal.

Added test coverage for all, including cases for full match, partial failure,
and empty input.