machine: rename machine_copy_from_to() -> machine_copy_from_to_operation()

This is done to make it clear that machine_copy_from_to() use and
returns an Operation object.

src/machine/machine-dbus.c

@@ -563,7 +563,7 @@ int bus_machine_method_copy(sd_bus_message *message, void *userdata, sd_bus_erro
         }
 
         Operation *op;
-        r = machine_copy_from_to(manager, m, host_path, container_path, copy_from, copy_flags, &op);
+        r = machine_copy_from_to_operation(manager, m, host_path, container_path, copy_from, copy_flags, &op);
         if (r < 0)
                 return sd_bus_error_set_errnof(error, r, "Failed to copy from/to machine '%s': %m", m->name);
 

src/machine/machine-varlink.c

@@ -913,7 +913,7 @@ int vl_method_copy_internal(sd_varlink *link, sd_json_variant *parameters, sd_va
                 return r;
 
         Operation *op;
-        r = machine_copy_from_to(manager, machine, host_path, container_path, copy_from, copy_flags, &op);
+        r = machine_copy_from_to_operation(manager, machine, host_path, container_path, copy_from, copy_flags, &op);
         if (r < 0)
                 return r;
 

src/machine/machine.c

@@ -954,7 +954,7 @@ char** machine_default_shell_args(const char *user) {
         return TAKE_PTR(args);
 }
 
-int machine_copy_from_to(
+int machine_copy_from_to_operation(
                 Manager *manager,
                 Machine *machine,
                 const char *host_path,

src/machine/machine.h

@@ -107,7 +107,7 @@ int machine_start_shell(Machine *m, int ptmx_fd, const char *ptmx_name, const ch
 #define machine_default_shell_path() ("/bin/sh")
 char** machine_default_shell_args(const char *user);
 
-int machine_copy_from_to(
+int machine_copy_from_to_operation(
                 Manager *manager,
                 Machine *machine,
                 const char *host_path,