kernel/fs: Introduce check_write_stat_permissions utility method.

Like check_access_permissions() but for write_stat() hook instead
of access().

Basic logic copied from BFS, but with the UID/GID logic rewritten
to better conform to behavior on other OSes: notably, we allow
chown() requests that keep the UID the same to go through, same
as Linux seems to, which should fix #19666. We now also validate
that the GID is one of the current team's groups.

headers/private/fs_shell/fssh_api_wrapper.h

@@ -950,6 +950,7 @@
 #define get_vnode_removed			fssh_get_vnode_removed
 #define volume_for_vnode			fssh_volume_for_vnode
 #define check_access_permissions	fssh_check_access_permissions
+#define check_write_stat_permissions fssh_check_write_stat_permissions
 #define read_pages					fssh_read_pages
 #define write_pages					fssh_write_pages
 #define read_file_io_vec_pages		fssh_read_file_io_vec_pages

headers/private/fs_shell/fssh_fs_interface.h

@@ -364,6 +364,9 @@ extern fssh_fs_volume* fssh_volume_for_vnode(fssh_fs_vnode *vnode);
 extern fssh_status_t fssh_check_access_permissions(int accessMode,
 				fssh_mode_t mode, fssh_gid_t nodeGroupID,
 				fssh_uid_t nodeUserID);
+extern fssh_status_t fssh_check_write_stat_permissions(fssh_gid_t nodeGroupID,
+				fssh_uid_t nodeUserID, fssh_mode_t nodeMode, uint32_t mask,
+				const struct fssh_stat* stat);
 
 extern fssh_status_t fssh_read_pages(int fd, fssh_off_t pos,
 				const struct fssh_iovec *vecs, fssh_size_t count,