vim-patch:9.1.1467: too many strlen() calls (#34572)

Problem:  too many strlen() calls
Solution: Change expand_env() to return string length
          (John Marriott)

This commit does the following changes:
- In expand_env_esc():
  - return the length of the returned dst string.
  - refactor to remove some calls to STRLEN() and STRCAT()
  - add check for out-of-memory condition.
- Change call sites in various source files to use the return value

closes: vim/vim#17561

fff0132399

Co-authored-by: John Marriott <basilisk@internode.on.net>

src/nvim/shada.c

@@ -1314,8 +1314,9 @@ static char *shada_filename(const char *file)
       //     because various expansions must have already be done by the shell.
       //     If shell is not performing them then they should be done in main.c
       //     where arguments are parsed, *not here*.
-      expand_env((char *)file, &(NameBuff[0]), MAXPATHL);
+      size_t len = expand_env((char *)file, &(NameBuff[0]), MAXPATHL);
       file = &(NameBuff[0]);
+      return xmemdupz(file, len);
     }
   }
   return xstrdup(file);