Button and color enhancements (#24989) (#25176)

Backport #24989. Clean cherry-pick aside from one small conflict with
divider.

- Various corrections to button styles, especially secondary
- Remove focus highlight, it's annoying when it stays on button after
press
- Clearly define ghost and link buttons with demos in devtest
- Remove black, grey and tertiary buttons, they should not be used
- Make `arc-green` slightly darker

<img width="1226" alt="image"

src="https://github.com/go-gitea/gitea/assets/115237/8d89786a-01ab-40f8-ae5a-e17f40e35084">
<img width="1249" alt="image"

src="https://github.com/go-gitea/gitea/assets/115237/83651e6d-3c27-46ff-b8bd-ff344d70e949">

templates/repo/view_file.tmpl

@@ -107,7 +107,7 @@
 						<tr>
 							<td id="L{{$line}}" class="lines-num"><span id="L{{$line}}" data-line-number="{{$line}}"></span></td>
 							{{if $.EscapeStatus.Escaped}}
-								<td class="lines-escape">{{if (index $.LineEscapeStatus $idx).Escaped}}<button class="toggle-escape-button button button-ghost" title="{{if (index $.LineEscapeStatus $idx).HasInvisible}}{{$.locale.Tr "repo.invisible_runes_line"}} {{end}}{{if (index $.LineEscapeStatus $idx).HasAmbiguous}}{{$.locale.Tr "repo.ambiguous_runes_line"}}{{end}}"></button>{{end}}</td>
+								<td class="lines-escape">{{if (index $.LineEscapeStatus $idx).Escaped}}<button class="toggle-escape-button btn interact-bg" title="{{if (index $.LineEscapeStatus $idx).HasInvisible}}{{$.locale.Tr "repo.invisible_runes_line"}} {{end}}{{if (index $.LineEscapeStatus $idx).HasAmbiguous}}{{$.locale.Tr "repo.ambiguous_runes_line"}}{{end}}"></button>{{end}}</td>
 							{{end}}
 							<td rel="L{{$line}}" class="lines-code chroma"><code class="code-inner">{{$code | Safe}}</code></td>
 						</tr>