basic/string-util: simplify how str_realloc() is used

All callers ignore failure anyway, so let's do that internally.

src/basic/process-util.c

@@ -179,7 +179,7 @@ int get_process_cmdline(pid_t pid, size_t max_columns, ProcessCmdlineFlags flags
         if (!ans)
                 return -ENOMEM;
 
-        (void) str_realloc(&ans);
+        ans = str_realloc(ans);
         *line = TAKE_PTR(ans);
         return 0;
 }

src/basic/string-util.h

@@ -217,17 +217,13 @@ static inline void *memory_startswith_no_case(const void *p, size_t sz, const ch
         return (uint8_t*) p + n;
 }
 
-static inline char* str_realloc(char **p) {
-        /* Reallocate *p to actual size */
+static inline char* str_realloc(char *p) {
+        /* Reallocate *p to actual size. Ignore failure, and return the original string on error. */
 
-        if (!*p)
+        if (!p)
                 return NULL;
 
-        char *t = realloc(*p, strlen(*p) + 1);
-        if (!t)
-                return NULL;
-
-        return (*p = t);
+        return realloc(p, strlen(p) + 1) ?: p;
 }
 
 char* string_erase(char *x);

src/basic/utf8.c

@@ -196,8 +196,7 @@ char *utf8_escape_invalid(const char *str) {
         }
 
         *s = '\0';
-        (void) str_realloc(&p);
-        return p;
+        return str_realloc(p);
 }
 
 static int utf8_char_console_width(const char *str) {
@@ -282,8 +281,7 @@ char *utf8_escape_non_printable_full(const char *str, size_t console_width) {
 
  finish:
         *s = '\0';
-        (void) str_realloc(&p);
-        return p;
+        return str_realloc(p);
 }
 
 char *ascii_is_valid(const char *str) {