Do some performance optimize for issues list and view issue/pull (#29515)

This PR do some performance optimzations.

- [x] Add `index` for the column `comment_id` of `Attachment` table to
accelerate query from the database.
- [x] Remove unnecessary database queries when viewing issues. Before
some conditions which id = 0 will be sent to the database
- [x] Remove duplicated load posters 
- [x] Batch loading attachements, isread of comments on viewing issue

---------

Co-authored-by: Zettat123 <zettat123@gmail.com>

models/migrations/v1_22/v291.go

@@ -0,0 +1,14 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_22 //nolint
+
+import "xorm.io/xorm"
+
+func AddCommentIDIndexofAttachment(x *xorm.Engine) error {
+	type Attachment struct {
+		CommentID int64 `xorm:"INDEX"`
+	}
+
+	return x.Sync(&Attachment{})
+}