Client customization late-join spawner priority for arrivals/cryostorage (#24586)

* Initial commit, requires server restart to take effect

* Exposes callbacks directly instead, takes effect immediately

* Cleaned up control flow, swapped cvar for client customization

* Switched to int, dictionary of callbacks, migration

* Update Content.Shared/Preferences/SpawnPriorityPreference.cs

* krunkle stan

---------

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Server.Database/Migrations/Postgres/20240201091301_SpawnPriorityPreference.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Content.Server.Database.Migrations.Postgres
+{
+    /// <inheritdoc />
+    public partial class SpawnPriorityPreference : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<int>(
+                name: "spawn_priority",
+                table: "profile",
+                type: "integer",
+                nullable: false,
+                defaultValue: 0);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "spawn_priority",
+                table: "profile");
+        }
+    }
+}