This commit makes the user-facing StdLibExtras templates and utilities
arguably more nice-looking by removing the need to reach into the
wrapper structs generated by them to get the value/type needed.
The C++ standard library had to invent `_v` and `_t` variants (likely
because of backwards compat), but we don't need to cater to any codebase
except our own, so might as well have good things for free. :^)
- The change to quick_sort requires SimpleIterator to support
assignment.
- Rename quick_sort to single_pivot_quick_sort to make it easier
to choose a specific implementation (not based on signature).
- Ensure single_pivot_quick_sort does not copy the pivots
- Expand sorts_without_copy test case to cover both single and dual
pivot implementations.
This gives the compiler enough information to optimize index validation
when using range-for to iterate over a Vector, drastically reducing the
cost of such loops.
