Port of 27354-navigation-new-button to EE

See merge request !1287

[ci skip]

[ci skip]

# Conflicts:
#	CHANGELOG.md

Merge branch '28769-raise-custom-exception-in-all-methods-of-mergeservice-that-want-to-inform-the-user-ee' into 'master'

Use exceptions for MergeService error handling

See merge request !1320

If any method called by `MergeService#execute` raises a `MergeError`,
that error's message will be logged, the model will be updated, and the
merge will fail.

CE upstream

Closes omnibus-gitlab#1361

See merge request !1319

Fix migration without DOWNTIME clause specified

See merge request !9571

Make RuboCop happy

See merge request !9554

Add button to create issue for failing build

Closes #25920

See merge request !9391

Fix inline comment images by removing wrapper #20890

Closes #20890

See merge request !5804

Fix broken dev environment in master

See merge request !9557

Keep consistent in handling indexOf results

Closes #28723

See merge request !9531

Add development fixtures for nested groups

See merge request !9553

Replace setInterval with setTimeout to prevent highly frequent requests

Closes #28212

See merge request !9271

[ci skip]

Fix #27840 - Improve the search bar experience on mobile

Closes #27840

See merge request !9280

[ci skip]

Removed jQuery UI draggable

See merge request !8582

CE Upstream - Friday

See merge request !1306

Fix webpack dev server when behind proxy

See merge request !9543

[ci skip]

Minor refactoring of Uploaders

See merge request !9490

Improve error messages when squashing fails

Closes gitlab-com/support-forum#1568

See merge request !1318

Match require statement. Status code is now undefined in master

See merge request !1314

[ci skip]

[ci skip]

Align last column buttons with new environment button

Closes #28753

See merge request !9551

Updates SSH key title after pasting key

Closes #28436

See merge request !9481

Add MockCiService integration

See merge request !1310

Add Mock CI service/integration

See merge request !9250

Fixed alignment of RSS button on activity pages

Closes #28572

See merge request !9478