libgpiosim: new testing library

I'm resending this with some improvements resulting from actual test writing with this library + with the right label this time.

This adds the library that talks to the new gpio-sim module. The module is not yet in any linux release so we'll update the kernel requirements once v5.17 is out.

The first patch adds the library and the second converts the C tests to using it.

The plan is to use it to completely rewrite the tests for v2 so I don't envision any more porting work for v1. Once we are on libgpiosim for all test frameworks in v2, we'll remove all gpio-mockup code from the project.

v1 -> v2:
- add new functions allowing to retrieve the parent dev of a bank and the parent context from a device
- add a function allowing to check if a device is live
- fix writing to configfs and sysfs attributes

Bartosz Golaszewski (2):
libgpiosim: new library for controlling the gpio-sim module
tests: port C tests to libgpiosim

 configure.ac                     |    7 +-
 tests/Makefile.am                |    8 +-
 tests/gpiod-test.c               |  143 +++--
 tests/gpiod-test.h               |    4 +-
 tests/gpiosim/.gitignore         |    4 +
 tests/gpiosim/Makefile.am        |   16 +
 tests/gpiosim/gpiosim-selftest.c |  157 +++++
 tests/gpiosim/gpiosim.c          | 1030 ++++++++++++++++++++++++++++++
 tests/gpiosim/gpiosim.h          |   69 ++
 9 files changed, 1391 insertions(+), 47 deletions(-)
 create mode 100644 tests/gpiosim/.gitignore
 create mode 100644 tests/gpiosim/Makefile.am
 create mode 100644 tests/gpiosim/gpiosim-selftest.c
 create mode 100644 tests/gpiosim/gpiosim.c
 create mode 100644 tests/gpiosim/gpiosim.h

2.30.1