Migrate MR and Pipeline status bar items to WebIDE
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Work on this issue](https://contributors.gitlab.com/manage-issue?action=work&projectId=278964&issueIid=415189)
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=415189)
</details>
<!--IssueSummary end-->
This issue si about migrating the MR and pipeline status bar items to `common` code

## Techincal details
The [`CurrentBranchReferesher`](https://gitlab.com/gitlab-org/gitlab-vscode-extension/blob/0588d5919a097d84466de0743fb8b016901fc34f/src/current_branch_refresher.ts#L70) is the data source for the "For Current Branch" panel:

It is now dependent on desktop-specific logic. We need to abstract all the dependencies to the `GitLabPlatform`, namely:
- We need to expose the current branch in the platform
- In desktop, we [read it from Git](https://gitlab.com/gitlab-org/gitlab-vscode-extension/blob/0588d5919a097d84466de0743fb8b016901fc34f/src/current_branch_refresher.ts#L143-162)
- In WebIDE, it's [coming from the config](https://gitlab.com/gitlab-org/gitlab-web-ide/blob/346fd036b76d15f8dc90b3e55947a7f27218ce0c/packages/web-ide-types/src/config.ts#L65-71)
- the tricky part is that (AFAIKT) if we open MR in the WebIDE, the `ref` config is empty (**needs verification**). That means we would have to get the branch from an MR
- another tricky part is that the WebIDE currently has a bug, and you can't open tags. The tags are handled differently in desktop Workflow
- All the GitLab service API calls (e.g. [getting pipeline and MR](https://gitlab.com/gitlab-org/gitlab-vscode-extension/blob/0588d5919a097d84466de0743fb8b016901fc34f/src/current_branch_refresher.ts#L146)) must be changed to use the new [`fetchFromApi` method](https://gitlab.com/gitlab-org/gitlab-vscode-extension/blob/0588d5919a097d84466de0743fb8b016901fc34f/src/code_suggestions/code_suggestions_token_manager.ts#L40)
## Progress:
@ealcantara and I were pairing on abstracting the API calls.
issue