libcamera: Standardise on C compatibility headers

Now that our usage of C compatibility header is documented, use them
consistently through the source code.

While at it, group the C and C++ include statements as defined in the
coding style, and fix a handful of #include ordering issues.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/log.cpp

@@ -7,14 +7,14 @@
 
 #include "log.h"
 
-#include <cstdio>
-#include <cstdlib>
-#include <ctime>
 #include <fstream>
 #include <iostream>
 #include <list>
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <syslog.h>
+#include <time.h>
 #include <unordered_set>
 
 #include <libcamera/logging.h>