[Feature Request] Analog sensitivity binds or "Sniper Mode"

Something that would make people with Analog-less controllers and Keyboard users happy is a way to change the sensitivity of the Analog Stick on the fly either by holding the button or as a toggle depending on preference.
This is a welcome feature seen in Project64 and it would be really nice to have here among other special custom binds.

This is especially necessary for certain N64 games, here are some notable examples:

• In Banjo-Tooie, sneaking is to be done with holding the stick forward very delicately.
• Yoshi's Story also requires sneaking in order to pass by bees (this one would also be nice for those who prefer Digital controls for 2D platformers!)
• In Banjo-Tooie, aiming the crosshair to the individual letters for cheato cheats is an absolute no-go (even with Analog controls it can be quite irritating from what I've been told).
• Aiming a cannon in Super Mario 64 can be a pain with Digital controls only.
• Aiming in general for Ocarina of Time is quite the dilemma without it, making the bow/slingshot minigame impossible on Keyboard.

The issue does not name files, tests, or entry points. Start by locating RetroArch's existing input-binding and analog-control handling, then determine how hold and toggle preferences would fit with custom binds. Done should include configurable sensitivity changes for keyboard and analog-less controller users, covering the listed aiming and sneaking scenarios.