stub: Remove monitor-fd.c

Both monitor-fd.c and monitor-internal.c contain a stub for
monitor_get_fd(), which causes a duplicate symbol linker error when
linking rust-qemu-api-integration. Use monitor-internal.c instead of
monitor-fd.c and remove the latter.

Reported-by: Zhao Liu <zhao1.liu@intel.com>
Suggested-by: Zhao Liu <zhao1.liu@intel.com>
Fixes: fccb744f41c6 ("gdbstub: Try unlinking the unix socket before binding")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250217104900.230122-1-iii@linux.ibm.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

stubs/meson.build

@@ -62,7 +62,7 @@ if have_user
     stub_ss.add(files('qdev.c'))
   endif
 
-  stub_ss.add(files('monitor-fd.c'))
+  stub_ss.add(files('monitor-internal.c'))
 endif
 
 if have_system

stubs/monitor-fd.c

@@ -1,9 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-
-#include "qemu/osdep.h"
-#include "monitor/monitor.h"
-
-int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp)
-{
-    abort();
-}