Vector algorithms with element size dispatch: standardize dispatching?

[AlexGuteniev]

Currently a scheme like __std_find_trivial -> __std_find_trivial_1/2/4/8 -> __std_find_trivial_impl
With these exceptions:

• Some like __std_reverse_trivially_swappable_1/2/4/8 don't have neither header dispatcher (so they are dispatched in multiple places), nor vector_algorithms.cpp common implementation
• Some .cpp implementations are unified under names _Minmax and _Minmax_element

Should we unify that?

[AlexGuteniev]

I propose the following:

• Unify .cpp names to _impl (including _Minmax_element -> _minmax_element_impl
• Don't unify whether there is common vector_algorithms.cpp implementation or not, keep this as it is
• Unify header dispatch to like _Find_trivial, so that _STD __std_find_trivial becomes _STD _Find_trivial and does not repeat "std"
• Unify to having header dispatch in a separate function if there are multiple usage and to not having it when there is a single usage

[StephanTLavavej]

We talked about this at the weekly maintainer meeting; Charlie Barto (@barcharcraz) and I agree with all of your proposals.