Timeline and color tweaks (#21799)

Followup to https://github.com/go-gitea/gitea/pull/21784.

- Restore muted effect on timeline author and issuelist comment icon
- Remove whitespace inside shared user templates, fixing link hover
underline
- Use shared author link template more
- Use `bold` class instead of CSS
- Fix grey-light color being too dark on arc-green
- Add missing black-light color
- Fix issuelist progress bar color
- Fix various other cases of missing `.muted`

<img width="416" alt="Screenshot 2022-11-13 at 12 15 22"
src="https://user-images.githubusercontent.com/115237/201519497-1d4725c6-bc8b-47b5-9f68-1278ac9a8c92.png">
<img width="324" alt="Screenshot 2022-11-13 at 12 16 52"
src="https://user-images.githubusercontent.com/115237/201519501-c0d03700-f9af-4316-ab46-482f2c7c738b.png">
<img width="79" alt="Screenshot 2022-11-13 at 12 30 55"
src="https://user-images.githubusercontent.com/115237/201519502-46dc2d73-bbdf-4a2e-84d3-d2976f793163.png">
<img width="440" alt="Screenshot 2022-11-13 at 12 41 03"
src="https://user-images.githubusercontent.com/115237/201519876-ada33948-f84a-4aeb-a40d-5c873f9a49e9.png">
<img width="213" alt="Screenshot 2022-11-13 at 12 52 54"
src="https://user-images.githubusercontent.com/115237/201520291-a4d7238e-aeca-46c7-9008-8b644b1b676e.png">
<img width="208" alt="Screenshot 2022-11-13 at 12 56 16"
src="https://user-images.githubusercontent.com/115237/201520436-aa8ba109-b959-42fb-831a-021e806c7082.png">

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/less/shared/issuelist.less

@@ -91,6 +91,14 @@
           border-radius: 3px;
           vertical-align: 2px !important;
         }
+
+        progress::-webkit-progress-value {
+          background-color: var(--color-secondary-dark-4);
+        }
+
+        progress::-moz-progress-bar {
+          background-color: var(--color-secondary-dark-4);
+        }
       }
 
       .conflicting {