Fix FilterCriteria only being able to support one tag filter at once

Other textual keyword filters also worked like that, wherein if you did
`artist=a artist=b` the second filter would overwrite the second, but in
those cases the query is against a single field, so attempting to put
multiple search criteria in conjunction on a single field is kind of
nonsensical, so it was sort of fine to do that.

Which is not the case for user tags, which are multi-valued.

osu.Game/Screens/Select/Carousel/CarouselBeatmap.cs

@@ -84,12 +84,17 @@ namespace osu.Game.Screens.Select.Carousel
             match &= !criteria.DifficultyName.HasFilter || criteria.DifficultyName.Matches(BeatmapInfo.DifficultyName);
             match &= !criteria.Source.HasFilter || criteria.Source.Matches(BeatmapInfo.Metadata.Source);
 
-            if (criteria.UserTag.HasFilter)
+            if (criteria.UserTags.Any())
             {
-                bool anyTagMatched = false;
-                foreach (string tag in BeatmapInfo.Metadata.UserTags)
-                    anyTagMatched |= criteria.UserTag.Matches(tag);
-                match &= anyTagMatched;
+                foreach (var tagFilter in criteria.UserTags)
+                {
+                    bool anyTagMatched = false;
+
+                    foreach (string tag in BeatmapInfo.Metadata.UserTags)
+                        anyTagMatched |= tagFilter.Matches(tag);
+
+                    match &= anyTagMatched;
+                }
             }
 
             match &= !criteria.UserStarDifficulty.HasFilter || criteria.UserStarDifficulty.IsInRange(BeatmapInfo.StarRating);

osu.Game/Screens/Select/FilterCriteria.cs

@@ -39,7 +39,7 @@ namespace osu.Game.Screens.Select
         public OptionalTextFilter Title;
         public OptionalTextFilter DifficultyName;
         public OptionalTextFilter Source;
-        public OptionalTextFilter UserTag;
+        public List<OptionalTextFilter> UserTags = [];
 
         public OptionalRange<double> UserStarDifficulty = new OptionalRange<double>
         {

osu.Game/Screens/Select/FilterQueryParser.cs

@@ -117,7 +117,10 @@ namespace osu.Game.Screens.Select
                     return TryUpdateCriteriaText(ref criteria.Source, op, value);
 
                 case "tag":
-                    return TryUpdateCriteriaText(ref criteria.UserTag, op, value);
+                    var tagFilter = new FilterCriteria.OptionalTextFilter();
+                    TryUpdateCriteriaText(ref tagFilter, op, value);
+                    criteria.UserTags.Add(tagFilter);
+                    return true;
 
                 default:
                     return criteria.RulesetCriteria?.TryParseCustomKeywordCriteria(key, op, value) ?? false;

osu.Game/Screens/SelectV2/BeatmapCarouselFilterMatching.cs

@@ -103,12 +103,17 @@ namespace osu.Game.Screens.SelectV2
             match &= !criteria.DifficultyName.HasFilter || criteria.DifficultyName.Matches(beatmap.DifficultyName);
             match &= !criteria.Source.HasFilter || criteria.Source.Matches(beatmap.Metadata.Source);
 
-            if (criteria.UserTag.HasFilter)
+            if (criteria.UserTags.Any())
             {
-                bool anyTagMatched = false;
-                foreach (string tag in beatmap.Metadata.UserTags)
-                    anyTagMatched |= criteria.UserTag.Matches(tag);
-                match &= anyTagMatched;
+                foreach (var tagFilter in criteria.UserTags)
+                {
+                    bool anyTagMatched = false;
+
+                    foreach (string tag in beatmap.Metadata.UserTags)
+                        anyTagMatched |= tagFilter.Matches(tag);
+
+                    match &= anyTagMatched;
+                }
             }
 
             match &= !criteria.UserStarDifficulty.HasFilter || criteria.UserStarDifficulty.IsInRange(beatmap.StarRating);