tree-wide: Make sure all headers are standalone

Let's make sure all of our headers include everything they require.

src/cryptsetup/cryptsetup-pkcs11.h

@@ -3,6 +3,7 @@
 
 #include <sys/types.h>
 
+#include "ask-password-api.h"
 #include "cryptsetup-util.h"
 #include "log.h"
 #include "time-util.h"

src/cryptsetup/cryptsetup-tokens/cryptsetup-token.h

@@ -1,6 +1,10 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
+#include <stddef.h>
+
+struct crypt_device;
+
 /* for more information see libcryptsetup.h crypt-tokens section */
 
 const char* cryptsetup_token_version(void);

src/cryptsetup/cryptsetup-tokens/luks2-pkcs11.h

@@ -2,6 +2,8 @@
 
 #pragma once
 
+#include <stddef.h>
+
 struct crypt_device;
 
 int acquire_luks2_key(