Fix tooltips and issue dependency styles (#13458)

- Convert all tooltips to JS-based ones, fixing overflow issues
- Restyle issue dependencies/dependants
- Move popup styles to base style
- CSS Helper tweaks
- Unify pseudo element selectors and lint for it

Fixes: https://github.com/go-gitea/gitea/issues/13400

.stylelintrc

@@ -11,5 +11,5 @@ rules:
   no-descending-specificity: null
   number-leading-zero: never
   rule-empty-line-before: null
-  selector-pseudo-element-colon-notation: null
+  selector-pseudo-element-colon-notation: double
   shorthand-property-no-redundant-values: true