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/file_info.tmpl

@@ -1,4 +1,4 @@
-<div class="file-info text grey normal mono">
+<div class="file-info text grey normal gt-mono">
 	{{if .FileIsSymlink}}
 		<div class="file-info-entry">
 			{{.locale.Tr "repo.symbolic_link"}}
@@ -16,7 +16,7 @@
 	{{end}}
 	{{if .LFSLock}}
 		<div class="file-info-entry ui tooltip" data-content="{{.LFSLockHint}}">
-			{{svg "octicon-lock" 16 "mr-2"}}
+			{{svg "octicon-lock" 16 "gt-mr-2"}}
 			<a href="{{.LFSLockOwnerHomeLink}}">{{.LFSLockOwner}}</a>
 		</div>
 	{{end}}