Add or resolve a to-do on tasks, objectives and key results
### Release notes
We know that GitLab [to-dos](https://docs.gitlab.com/ee/user/todos.html#to-do-list) are a widely adopted feature but were not available on tasks, objectives and key results. With this work, we will introduce the ability to toggle a to-do on/off from a work item record.

## Problem
You can't resolve a todo or add a todo manually within a work item.
## Proposal
Provide a mechanism to add or resolve a todo within the work item detail view.
## Design
#### Record view
|No to-do selected |to-do selected |
|---|---|
|||
#### Modal view
|No to-do selected |to-do selected |
|---|---|
|||
## Acceptance
- [x] Add Todo
- [x] Mark Todo as resolved
- [ ] Redis counter
- [ ] Todos update in real-time
## Redis Counter
<details>
<summary>create internal note:</summary>
* **name:** `users_resolving_todo`
* **category:** `work_items`
* **redis_slot:** `users`
* **include in the following aggregation counters:**
* [x] `xmau_plan`
* [x] `xmau_project_management`
* [ ] `xmau_product_planning`
* [ ] `xmau_certify`
* [x] `users_work_items`
* **documentation:** [Service Ping Implementation](https://docs.gitlab.com/ee/development/service_ping/implement.html), [Redis HLL Counters](https://docs.gitlab.com/ee/development/service_ping/implement.html#redis-hll-counters), [Plan's Redis HLL Schema / Approach](https://gitlab.com/gitlab-org/gitlab/-/issues/346046)
</details>
epic