gpio-sim

**Is your feature request related to a problem? Please describe.**
I have to re-compile the kernel to use this feature (gpio-sim). My need is to mock-up gpio signals at a very low level to keep the source code consistent.

**Describe the solution you'd like**
The kernel to already have this module.

**Describe alternatives you've considered**
Mocking-up gpio signals with other modules. However, eventually all got deprecated or need constant changes to keep them updated.

**Additional context**
No additional context.

The issue names no files, tests, or entry points. Start by investigating how WSL configures its Linux kernel modules and whether gpio-sim can be included without recompilation; done would mean the module is available by default.

Written by the indexing model from the issue text.