Remove migrations prior to 1.0.3.162 (#5939)

* Consolidate EF migrations up to 03/2020 into a single SQL script

* Remove old migrations code

BTCPayServer.Data/DBScriptsMigration.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace BTCPayServer.Data
+{
+    public abstract class DBScriptsMigration : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            foreach (var script in GetType().GetCustomAttributes<DBScriptAttribute>().OrderBy(n => n.ScriptName))
+            {
+                var name = Assembly.GetExecutingAssembly().GetManifestResourceNames()
+                    .First(s => s.EndsWith("." + script.ScriptName, StringComparison.Ordinal));
+                var stream = Assembly.GetExecutingAssembly()
+                            .GetManifestResourceStream(name);
+                using var reader = new StreamReader(stream, Encoding.UTF8);
+                migrationBuilder.Sql(reader.ReadToEnd());
+            }
+        }
+    }
+
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
+    public class DBScriptAttribute : Attribute
+    {
+        public DBScriptAttribute(string scriptName)
+        {
+            ScriptName = scriptName;
+        }
+        public string ScriptName { get; set; }
+    }
+}