Show messages when pet is captured or released

When using a pet carrier to capture or release a pet, it was not
displaying any kind of success message in the log. Now you will get i.e.

    "You capture the cat in your pet carrier."
    "You release the cat."

Following the example of similar log messages in these functions, I
added one message for successful capture, and one for successful
release.

This commit was going to be a simple two-line addition, but I discovered
that `release_monster` was deleting the name of the contained animal as
part of releaseing it, thus I got an empty string when trying to log it.

The solution, setting a local `contained_name` variable to remember the
animal name, had a nice side-effect of making several other lines a
little cleaner and more readable after slight refactoring, so I am
including that too.

src/iuse.cpp

@@ -9252,6 +9252,9 @@ int iuse::capture_monster_act( player *p, item *it, bool, const tripoint &pos )
         return 0;
     }
     if( it->has_var( "contained_name" ) ) {
+        // Remember contained_name for messages after release_monster erases it
+        const std::string contained_name = it->get_var( "contained_name", "" );
+
         if( it->release_monster( pos ) ) {
             // It's been activated somewhere where there isn't a player or monster, good.
             return 0;
@@ -9260,21 +9263,19 @@ int iuse::capture_monster_act( player *p, item *it, bool, const tripoint &pos )
             if( it->release_monster( p->pos(), 1 ) ) {
                 return 0;
             }
-            p->add_msg_if_player( _( "There is no place to put the %s." ),
-                                  it->get_var( "contained_name", "" ) );
+            p->add_msg_if_player( _( "There is no place to put the %s." ), contained_name );
             return 0;
         } else {
-            const std::string query = string_format( _( "Place the %s where?" ),
-                                      it->get_var( "contained_name", "" ) );
+            const std::string query = string_format( _( "Place the %s where?" ), contained_name );
             const cata::optional<tripoint> pos_ = choose_adjacent( query );
             if( !pos_ ) {
                 return 0;
             }
             if( it->release_monster( *pos_ ) ) {
+                p->add_msg_if_player( _( "You release the %s." ), contained_name );
                 return 0;
             }
-            p->add_msg_if_player( m_info, _( "You cannot place the %s there!" ),
-                                  it->get_var( "contained_name", "" ) );
+            p->add_msg_if_player( m_info, _( "You cannot place the %s there!" ), contained_name );
             return 0;
         }
     } else {
@@ -9311,6 +9312,8 @@ int iuse::capture_monster_act( player *p, item *it, bool, const tripoint &pos )
             // If the monster is friendly, then put it in the item
             // without checking if it rolled a success.
             if( f.friendly != 0 || one_in( chance ) ) {
+                p->add_msg_if_player( _( "You capture the %1$s in your %2$s." ),
+                                      f.type->nname(), it->tname() );
                 return it->contain_monster( target );
             } else {
                 p->add_msg_if_player( m_bad, _( "The %1$s avoids your attempts to put it in the %2$s." ),