Run clang-format and enable CI check for it (#755)

* pre-commit: Update and enable clang-format check

There is newer version from clang-format so use that. We do not yet want
18 as that is little bit too new.

* Format some thing by hand which clang-format "breaks"

Clang-format will format some things little bit off in some cases.
Format some things by hand so we get cleaner end result.

* Run clang-format with

```
pre-commit run --all-files clang-format
```

We have already in previously checked places where clang-format does not
make good format and ignored those (hopefully most of the things).

---------

Co-authored-by: Kari Argillander <kari.argillander@fidelix.com>

apps/gateway/gateway.h

@@ -18,9 +18,9 @@
 
 /* Device configuration definitions. */
 #define FIRST_DEVICE_NUMBER 260001
-#define VIRTUAL_DNET  2709      /* your choice of number here */
+#define VIRTUAL_DNET 2709 /* your choice of number here */
 #define DEV_NAME_BASE "Gateway Demo Device"
 #define DEV_DESCR_GATEWAY "Gateway Device and Router"
-#define DEV_DESCR_REMOTE  "Routed Remote Device"
+#define DEV_DESCR_REMOTE "Routed Remote Device"
 
 #endif