Use data-tooltip-content for tippy tooltip (#23649)

Follow:
* #23574
* Remove all ".tooltip[data-content=...]"

Major changes:

* Remove "tooltip" class, use "[data-tooltip-content=...]" instead of
".tooltip[data-content=...]"
* Remove legacy `data-position`, it's dead code since last Fomantic
Tooltip -> Tippy Tooltip refactoring
* Rename reaction attribute from `data-content` to
`data-reaction-content`
* Add comments for some `data-content`: `{{/* used by the form */}}`
* Remove empty "ui" class
* Use "text color" for SVG icons (a few)

templates/repo/cite/cite_buttons.tmpl

@@ -6,6 +6,6 @@ BibTeX
 </button>
 <!-- the value will be updated by initCitationFileCopyContent, the code below is used to avoid UI flicking  -->
 <input id="citation-copy-content" value="" size="1" readonly>
-<button class="ui basic icon button tooltip" id="citation-clipboard-btn" data-content="{{.locale.Tr "copy"}}" data-clipboard-text="" data-clipboard-target="#citation-copy-content">
+<button class="ui basic icon button" id="citation-clipboard-btn" data-tooltip-content="{{.locale.Tr "copy"}}" data-clipboard-text="" data-clipboard-target="#citation-copy-content">
 	{{svg "octicon-copy"}}
 </button>

templates/repo/cite/cite_modal.tmpl

@@ -7,7 +7,7 @@
 			<div class="fitted item">
 				<div class="ui action input" id="citation-panel">
 					{{template "repo/cite/cite_buttons" .}}
-					<a id="goto-citation-btn" class="ui basic jump icon button tooltip" href="{{$.RepoLink}}/src/{{$.BranchName}}/CITATION.cff" data-position="top right" data-content="{{.locale.Tr "repo.find_file.go_to_file"}}">
+					<a id="goto-citation-btn" class="ui basic jump icon button" href="{{$.RepoLink}}/src/{{$.BranchName}}/CITATION.cff" data-tooltip-content="{{.locale.Tr "repo.find_file.go_to_file"}}">
 						{{svg "octicon-file-moved"}}
 					</a>
 				</div>