Draft: Resolve "Highlight design comment when coming from TODO"

What does this MR do?

This MR simplifies data flow for updating the active discussion in Design Management.

Previously, everywhere where we wanted to update the active discussion, we would simply call the client Apollo mutation. The one issue with this approach is that, ideally, we want to keep the URL hash in sync with these mutations. Setting the hash in the mutation's resolver would work, however would introduce a side-effect into the resolver, which we want to avoid.

This MR uses the URL hash as the source of truth for the active discussion; when the hash is updated, we update our Apollo cache (via the updateActiveDiscussion mutation).

Resolves:

• #225987 (closed)
• #229136

Screenshots

TBC

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