ostree_kernel_args_contains for OstreeKernelArgs

Check if an argument is present in OstreeKernelArgs. This is a way to
make easier idempotent append and delete operations.
ostree_kernel_args_append_if_missing uses it to avoid inserting a
duplicate key.

Closes #2329

Signed-off-by: Rafael Garcia Ruiz <rafael.garcia@collabora.com>

rust-bindings/sys/src/lib.rs

@@ -1313,6 +1313,12 @@ extern "C" {
     #[cfg(any(feature = "v2022_5", feature = "dox"))]
     #[cfg_attr(feature = "dox", doc(cfg(feature = "v2022_5")))]
     pub fn ostree_kernel_args_append_if_missing(kargs: *mut OstreeKernelArgs, arg: *const c_char);
+    #[cfg(any(feature = "v2022_7", feature = "dox"))]
+    #[cfg_attr(feature = "dox", doc(cfg(feature = "v2022_7")))]
+    pub fn ostree_kernel_args_contains(
+        kargs: *mut OstreeKernelArgs,
+        arg: *const c_char,
+    ) -> gboolean;
     #[cfg(any(feature = "v2019_3", feature = "dox"))]
     #[cfg_attr(feature = "dox", doc(cfg(feature = "v2019_3")))]
     pub fn ostree_kernel_args_append_proc_cmdline(