Mapping fixes

* Store type lookup is now case-insensitive
* Fixed NpgsqlTimeTypeMapping to map to TimeSpan, not DateTime

src/EFCore.PG/Storage/Internal/Mapping/NpgsqlDateTimeTypeMapping.cs

 using System;
 using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
 using NpgsqlTypes;
+using Remotion.Linq.Clauses.Expressions;
 
 namespace Microsoft.EntityFrameworkCore.Storage.Internal.Mapping
 {
@@ -55,10 +56,15 @@ protected override string GenerateNonNullSqlLiteral(object value)
 
     public class NpgsqlTimeTypeMapping : NpgsqlTypeMapping
     {
-        public NpgsqlTimeTypeMapping() : base("time without time zone", typeof(DateTime), NpgsqlDbType.Time) {}
+        public NpgsqlTimeTypeMapping() : base("time without time zone", typeof(TimeSpan), NpgsqlDbType.Time) {}
 
         protected override string GenerateNonNullSqlLiteral(object value)
-            => $"TIME '{(DateTime)value:HH:mm:ss.FFF}'";
+        {
+            var ts = (TimeSpan)value;
+            return ts.Milliseconds == 0
+                ? $@"TIME '{(TimeSpan)value:hh\:mm\:ss}'"
+                : $@"TIME '{(TimeSpan)value:hh\:mm\:ss\.FFF}'";
+        }
     }
 
     public class NpgsqlTimeTzTypeMapping : NpgsqlTypeMapping

src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs

@@ -219,7 +219,7 @@ public class NpgsqlTypeMappingSource : RelationalTypeMappingSource
                 { typeof(NpgsqlRange<DateTime>),      _tsrange     }
             };
 
-            _storeTypeMappings = new ConcurrentDictionary<string, RelationalTypeMapping>(storeTypeMappings);
+            _storeTypeMappings = new ConcurrentDictionary<string, RelationalTypeMapping>(storeTypeMappings, StringComparer.OrdinalIgnoreCase);
             _clrTypeMappings = new ConcurrentDictionary<Type, RelationalTypeMapping>(clrTypeMappings);
 
             if (typeof(NpgsqlConnection).Assembly.GetName().Version < new Version(3, 3))