Add attachment support for code review comments (#29220)

Fixes #27960, #24411, #12183

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/diff/box.tmpl

@@ -237,6 +237,11 @@
 					"TextareaName" "content"
 					"DropzoneParentContainer" ".ui.form"
 				)}}
+				{{if .IsAttachmentEnabled}}
+					<div class="field">
+						{{template "repo/upload" .}}
+					</div>
+				{{end}}
 				<div class="text right edit buttons">
 					<button class="ui cancel button">{{ctx.Locale.Tr "repo.issues.cancel"}}</button>
 					<button class="ui primary save button">{{ctx.Locale.Tr "repo.issues.save"}}</button>