global: remove unnecessary includes from headers.

Each header should only include the other headers it needs to compile;
`devtools/reduce-includes.sh */*.h` does this.  The C files then need
additional includes if they don't compile.

And remove the entirely useless wire/onion_wire.h, which only serves to include wire/onion_wiregen.h.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

plugins/keysend.c

@@ -4,11 +4,14 @@
 #include <ccan/asort/asort.h>
 #include <ccan/cast/cast.h>
 #include <ccan/tal/str/str.h>
+#include <common/features.h>
 #include <common/gossmap.h>
 #include <common/json_param.h>
 #include <common/json_stream.h>
 #include <common/memleak.h>
 #include <errno.h>
+#include <inttypes.h>
+#include <plugins/channel_hint.h>
 #include <plugins/libplugin-pay.h>
 #include <sodium.h>