Issue relative position scope in group boards does not include projects in subgroups

What does this MR do?

#13254 (closed)

Fixes following method in EE::Issue

# Issue position on boards list should be relative to all group projects
def parent_ids
  return super unless has_group_boards?

  board_group.projects.select(:id)
end

Replacing with board_group.all_projects.select(:id) to include projects in subgroups. When using projects, the relative position of an issue would be calculated without considering projects in subgroups and would result in issues reordered in unexpected ways.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] ~~Label as security and @ mention @gitlab-com/gl-security/appsec~~
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] ~~Security reports checked/validated by a reviewer from the AppSec team ~~

Closes #13254 (closed)