Expose hide_backlog_list and hide_closed_list to boards REST API

What does this MR do?

• Move "Update a group board API" endpoint to Core (already in Core via WebUI)
• Expose hide_backlog_list and hide_closed_list to project and group boards API

Also, some refactor:

• Reduce the differences between project and group boards (no change)
• Refactor board update parameters (no effective change)

Some other missing pieces that this MR doesn't fix:

• Also accept hide_backlog_list and hide_closed_list (and assignee_id, milestone_id, labels and weight if EE) to the create dashboard API
• Allow to create group dashboard via API in CE, when there is none. Or maybe move multiple group boards to CE?

See gitlabracadabra/gitlabracadabra!85 (merged) for context.

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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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