Move helpers to be prefixed with gt- (#22879)

As discussed in #22847 the helpers in helpers.less need to have a
separate prefix as they are causing conflicts with fomantic styles

This will allow us to have the `.gt-hidden { display:none !important; }`
style that is needed to for the reverted PR.

Of note in doing this I have noticed that there was already a conflict
with at least one chroma style which this PR now avoids.

I've also added in the `gt-hidden` style that matches the tailwind one
and switched the code that needed it to use that.

Signed-off-by: Andrew Thornton <art27@cantab.net>

---------

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/diff/comments.tmpl

@@ -8,10 +8,10 @@
 		{{template "shared/user/avatarlink" .Poster}}
 	{{end}}
 	<div class="content comment-container">
-		<div class="ui top attached header comment-header df ac sb">
-			<div class="comment-header-left df ac">
+		<div class="ui top attached header comment-header gt-df gt-ac gt-sb">
+			<div class="comment-header-left gt-df gt-ac">
 				{{if .OriginalAuthor}}
-					<span class="text black bold mr-2">
+					<span class="text black gt-bold gt-mr-2">
 						{{svg (MigrationIcon $.root.Repository.GetOriginalURLHostname)}}
 						{{.OriginalAuthor}}
 					</span>
@@ -30,7 +30,7 @@
 					</span>
 				{{end}}
 			</div>
-			<div class="comment-header-right actions df ac">
+			<div class="comment-header-right actions gt-df gt-ac">
 				{{if and .Review}}
 					{{if eq .Review.Type 0}}
 						<div class="ui label basic small yellow pending-label tooltip" data-content="{{$.root.locale.Tr "repo.issues.review.pending.tooltip" ($.root.locale.Tr "repo.diff.review") ($.root.locale.Tr "repo.diff.review.approve") ($.root.locale.Tr "repo.diff.review.comment") ($.root.locale.Tr "repo.diff.review.reject")}}">