Make per-core button mapping more user-friendly and less counter-intutive.

First and foremost consider this:

• Only RetroArch bugs should be filed here. Not core bugs or game bugs
• This is not a forum or a help section, this is strictly developer oriented

Description

Per core button mapping is not user friendly. It is counterintuitive.

Expected behavior

Start with a list of game buttons on the left (for N64 this would be Analog UDLR, D-Pad UDLR, C UDLR, A, B, L, R, Z, and Start) - selecting one of which would either allow you to press one or more buttons and have that selection be chosen.

Actual behavior

Left side is a list of buttons mapped to a controller for a PSX style setup that had been previously mapped, upon selecting one of these you have a list of buttons for the selected core. Chose the correct one. Hope for the best.

Steps to reproduce the bug

Map an N64 controller in the main input menu in some manner. This input menu expects a Dual Shock style controller.
Load a core (Mupen64 in my case).
Try and play a game.
Notice that none of the buttons do as expected.
Search internet for results.
Try several things.
Eventually (took me 10+ tries) get it to work.

Bisect Results

As far as I'm aware, this has been a problem for as long as retroarch has existed.

Version/Commit

You can find this information under Information/System Information

• RetroArch: 1.10.0 (Steam)

Environment information

• OS: Pop!_OS 21.10.
• Compiler: [In case you are running local builds]

Start with the main input menu and the per-core button-mapping flow, reproducing the issue with an N64 game and the Mupen64 core. Compare the current controller-oriented choices with the requested game-button-oriented flow; done means N64 mappings can be selected intuitively and produce the expected in-game buttons.