refactor: iwyu string, vector, cstdint (#2898)

* refactor: use cstdint for intX_t types

* refactor: iwyu sstring_view

* refactor: iwyu <cstring>

* refactor: iwyu <vector>

daemon/daemon-posix.cc

@@ -11,6 +11,8 @@
 #include <fcntl.h> /* open() */
 #include <unistd.h> /* fork(), setsid(), chdir(), dup2(), close(), pipe() */
 
+#include <string_view>
+
 #include <fmt/format.h>
 
 #include <libtransmission/transmission.h>