This reverts merge request !1426

Port of 27376-cache-default-branch-pipeline-on-project to EE

See merge request !1426

Fix rake gitlab:env:info elasticsearch datum

Closes #1164

See merge request !1422

Port of issue-boards-new-search-bar to EE

See merge request !1397

Updated issue boards

See merge request !1419

[ci skip]

Fix rollback for an EE migration

See merge request !1425

Move the index removal to be before the column removal

Resolve "Use the v4 API from the frontend"

Closes #1849

See merge request !1373

[EE] Remove explicit `require` calls, and use `require_dependency` when needed

See merge request !1413

The update includes the change to multiple issue boards that can have a milestone

Update github.md

See merge request !1418

This saves pushing the state & creating a new history entry

Fixed eslint

Changed an isArray check to use -1
Added comment to boards search manager to explain behaviour

This includes elements not being on the page & various store states needing updated

Port of 'remove-iifes-1' to EE

See merge request !1415

Fixed multiple boards new form scrolling

Closes #1897

See merge request !1414