Fix issue title rendering and refactor legacy function names (#32703)

Fix #32700, regression of recent markup refactoring

And by the way, clarify many legacy problems:

1. Some "RenderXxx" functions do not really "render", they only call "post processors"
2. Merge "RenderEmoji | RenderCodeBlock", they are all for "simple issue title"

templates/repo/diff/compare.tmpl

@@ -187,7 +187,7 @@
 			<div class="ui segment flex-text-block tw-gap-4">
 				{{template "shared/issueicon" .}}
 				<div class="issue-title tw-break-anywhere">
-					{{ctx.RenderUtils.RenderIssueTitle .PullRequest.Issue.Title ($.Repository.ComposeMetas ctx) | RenderCodeBlock}}
+					{{ctx.RenderUtils.RenderIssueTitle .PullRequest.Issue.Title ($.Repository.ComposeMetas ctx)}}
 					<span class="index">#{{.PullRequest.Issue.Index}}</span>
 				</div>
 				<a href="{{$.RepoLink}}/pulls/{{.PullRequest.Issue.Index}}" class="ui compact button primary">