Issue and Pulls lists rework (#13594)

* Issue and Pulls lists rework

Reorganized and restyled the issue and pull request lists.

* color and layout tweaks

* use new issue list on dashboard as well

* move pagination into template

* misc tweaks

* fix label hover

* fix milestone list

* fix discrepancies between issue and milestone list, add new 'merge' helper

* fmt

* simplify merge helper

* remove whitespace

* fix startIndex

* further simplify dict merging

* rename helper to 'mergeinto' for clarity

* allow bottom-row to wrap

Co-authored-by: Lauris BH <lauris@nix.lv>

web_src/less/helpers.less

@@ -6,6 +6,7 @@
 .sb { justify-content: space-between !important; }
 .fc { flex-direction: column !important; }
 .f1 { flex: 1 !important; }
+.fw { flex-wrap: wrap !important; }
 
 .mono {
   font-family: var(--fonts-monospace) !important;