tree-wide: move unsigned to the start of type declaration

Even though ISO C11 doesn't mandate in which order the type specifiers
should appear, having `unsigned` at the beginning of each type
declaration feels more natural and, more importantly, it unbreaks
Coccinelle, which has a hard time parsing `long unsigned` and others:

```
init_defs_builtins: /usr/lib64/coccinelle/standard.h
init_defs: /home/mrc0mmand/repos/systemd/coccinelle/macros.h
HANDLING: src/shared/mount-util.c
: 1: strange type1, maybe because of weird order: long unsigned
```

Most of the codebase already "complies", so let's fix the remaining
"offenders".

src/test/test-mountpoint-util.c

@@ -18,7 +18,7 @@
 #include "tmpfile-util.h"
 
 static void test_mount_propagation_flags_one(const char *name, int ret, unsigned long expected) {
-        long unsigned flags;
+        unsigned long flags;
 
         log_info("/* %s(%s) */", __func__, name);
 

src/test/test-sizeof.c

@@ -53,8 +53,8 @@ int main(void) {
         info(unsigned char);
         info(short unsigned);
         info(unsigned);
-        info(long unsigned);
-        info(long long unsigned);
+        info(unsigned long);
+        info(unsigned long long);
         info(__syscall_ulong_t);
         info(__syscall_slong_t);
         info(intmax_t);