Add unique validation for environment_scope in clusters. Add on_environment scope for clusters. Add tests

Create has_environment_scope for centerlizing env_scope specific process. Pass environment_scope to  deployment_platform method.

Port of Resolve "Display member role per project" to EE

See merge request gitlab-org/gitlab-ee!3525

Port from CE: The API isn't using the appropriate services for managing forks

Closes gitlab-ce#40752

See merge request gitlab-org/gitlab-ee!3659

Updated geo-overview.png

Closes #4106

See merge request gitlab-org/gitlab-ee!3650

List multiple clusters EE

Closes #3734

See merge request gitlab-org/gitlab-ee!3644

Simplifying the configuration page

See merge request gitlab-org/gitlab-ee!3599

Merge branch '4242-failure-in-spec-ee-spec-services-ee-projects-hashed_storage-migrate_attachments_service_spec-rb' into 'master'

Resolve "Failure in spec/ee/spec/services/ee/projects/hashed_storage/migrate_attachments_service_spec.rb"

See merge request gitlab-org/gitlab-ee!3653

[EE] Move the "Limit conflicts with EE" doc to "Automatic CE-> EE merge"

See merge request gitlab-org/gitlab-ee!3658

Add example with number and parentheses

See merge request gitlab-org/gitlab-ee!3649

Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix board filter when milestone is  predefined

Closes gitlab-ce#40654

See merge request gitlab-org/gitlab-ee!3605