Move code indexer related code to a new package (#9191)

* move code indexer related code to a new package

* fix lint

* fix tests

* fix fmt

* GetMaxID support interface parameter

modules/indexer/code/bleve_test.go

@@ -0,0 +1,16 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package code
+
+import (
+	"path/filepath"
+	"testing"
+
+	"code.gitea.io/gitea/models"
+)
+
+func TestMain(m *testing.M) {
+	models.MainTest(m, filepath.Join("..", "..", ".."))
+}