Merge branch 'issue-boards-large-height-load' into 'master'

Fixed issue boards loading issues on large screens

## What does this MR do?

On larger screens it is possible for 20 issues to load (this is the amount per page) & there still to be room underneath the last issue which means the list can't scroll stopping the infinite scrolling working.

This MR checks if there are more issues to load, if there are & the height of the scroll area is less than or the same as scroll height then more issues are loaded. This will keep happening until it is possible to scroll, once it is possible to scroll it goes back to the default behaviour of the infinite scrolling.

## What are the relevant issue numbers?

Closes #22092

See merge request !6319

CHANGELOG

@@ -63,6 +63,7 @@ v 8.12.0 (unreleased)
   - Use 'git update-ref' for safer web commits !6130
   - Sort pipelines requested through the API
   - Automatically expand hidden discussions when accessed by a permalink !5585 (Mike Greiling)
+  - Fix issue boards loading on large screens
   - Change pipeline duration to be jobs running time instead of simple wall time from start to end !6084
   - Show queued time when showing a pipeline !6084
   - Remove unused mixins (ClemMakesApps)

app/assets/javascripts/boards/components/board_list.js.es6

@@ -34,6 +34,11 @@
       },
       issues () {
         this.$nextTick(() => {
+          if (this.scrollHeight() <= this.listHeight() && this.list.issuesSize > this.list.issues.length) {
+            this.list.page++;
+            this.list.getIssues(false);
+          }
+
           if (this.scrollHeight() > this.listHeight()) {
             this.showCount = true;
           } else {