basic: Move assertion specific functions to assert-util.h

Various functions in log.h are only used by asserts, and there's
enough assertion related stuff in macro.h to justify a separate header
which also makes it easier to avoid circular dependencies.

Let's introduce assert-util.h and an accompanying fundamental header
and move all the assertion related stuff over there. PROJECT_FILE is
moved over to macro.h.

src/shared/fstab-util.h

@@ -4,6 +4,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+#include "assert-util.h"
 #include "macro.h"
 
 bool fstab_enabled_full(int enabled);

src/shared/osc-context.h

@@ -3,6 +3,7 @@
 
 #include "sd-id128.h"
 
+#include "assert-util.h"
 #include "macro.h"
 
 int osc_context_open_boot(char **ret_seq);

src/shared/pretty-print.h

@@ -2,6 +2,7 @@
 #pragma once
 
 #include "ansi-color.h"
+#include "assert-util.h"
 #include "glyph-util.h"
 #include "terminal-util.h"