gpioioctl: Improve Registration

[gsexton]

Fixes #62

GPIO Chips with labels pinctrl-* are sorted to register first. This is a kernel convention identifying a GPIO chip that has exported/user lines.

Handling for potential duplicate chips was added. The kernel is exporting gpiochip0, and symlinking it to gpiochip4 as well. This PR ensures a chip with the same name is not registered more than once.

Cleaned up some code duplication in the basic test.

If the registration code detects that a line is already registered, it attempts to make the line name unique by prefixing it with the chip name.

Tested on a Pi5, and a Pi Zero W.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 56 lines in your changes missing coverage. Please review.

Project coverage is 27.3%. Comparing base (75941b8) to head (9d985ec).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
gpioioctl/gpio.go	0.0%	56 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main     #64     +/-   ##
=======================================
- Coverage   27.4%   27.3%   -0.1%     
=======================================
  Files         96      96             
  Lines      11774   11815     +41     
=======================================
- Hits        3221    3220      -1     
- Misses      8418    8460     +42     
  Partials     135     135             

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[gsexton]

@maruel Not sure why this is failing. It doesn't look like something I did...

[maruel]

Thanks a lot. Everything is stylistic and optional except line 626 where it could be a real crash.

[maruel]

Thanks again!