Expose no-op constructors as protected

[peppy]

This allows bypassing the population of Guid based IDs, which can have considerable overhead in batch usage cases, where we are 100% sure we aren't ever storing to realm:

Consumption looks like this:

diff --git a/osu.Server.Queues.ScoreStatisticsProcessor/Models/SoloScore.cs b/osu.Server.Queues.ScoreStatisticsProcessor/Models/SoloScore.cs
index a649708..260ad39 100644
--- a/osu.Server.Queues.ScoreStatisticsProcessor/Models/SoloScore.cs
+++ b/osu.Server.Queues.ScoreStatisticsProcessor/Models/SoloScore.cs
@@ -84,19 +84,20 @@ namespace osu.Server.Queues.ScoreStatisticsProcessor.Models
         public ScoreInfo ToScoreInfo()
         {
             var ruleset = LegacyRulesetHelper.GetRulesetFromLegacyId(ruleset_id);
+            var beatmapInfo = new LightweightBeatmapInfo
+            {
+                OnlineID = (int)beatmap_id,
+                Ruleset = new RulesetInfo { OnlineID = beatmap!.playmode }
+            };
 
-            return new ScoreInfo
+            return new LightweightScoreInfo
             {
                 OnlineID = (long)id,
                 LegacyOnlineID = (long?)legacy_score_id ?? -1,
                 IsLegacyScore = is_legacy_score,
                 User = new APIUser { Id = (int)user_id },
-                BeatmapInfo = new BeatmapInfo
-                {
-                    OnlineID = (int)beatmap_id,
-                    Ruleset = new RulesetInfo { OnlineID = beatmap!.playmode }
-                },
                 Ruleset = new RulesetInfo { OnlineID = ruleset_id },
+                BeatmapInfo = beatmapInfo,
                 Passed = passed,
                 TotalScore = total_score,
                 LegacyTotalScore = legacy_total_score,
@@ -112,5 +113,13 @@ namespace osu.Server.Queues.ScoreStatisticsProcessor.Models
                 Ranked = ranked,
             };
         }
+
+        private class LightweightBeatmapInfo : BeatmapInfo
+        {
+        }
+
+        private class LightweightScoreInfo : ScoreInfo
+        {
+        }
     }
 }

[bdach]

These sorts of changes always make me a bit nervous, but upon looking at things I believe it should be fine, because:

• When realm is actually present (i.e. client-side), deriving from both of these classes is not allowed and fody will loudly protest about it.
• The ctor is still protected, which means there should be no surprises like some usage suddenly switching from the ctor with multiple params with defaults to the true parameterless one.

And looking at IL with the patch applied it does look like this would skip the guid initialisation.