Add additional source control operations to the Web IDE
## Problem to solve
Our implementation of source control in the Web IDE is based on the GitLab API and not a full `git` workflow. It does not support more advanced git operations.
## Proposal
Add the ability to perform other git operations in the Web IDE. Start with the following:
1. [Pull](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/479)
2. [Checkout to...](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/480)
3. [Commit](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/482)
1. Commit & Push
2. Amend commit & force push
3. Commit & force push
4. [Changes](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/476)
1. Stage all changes
2. Unstage all changes
3. Discard all changes
4. Commit staged
5. [Branch](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/478)
1. Create branch...
2. Create branch from...
3. Delete branch...
6. [Stash](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/477)
1. Stash
2. Apply latest stash
3. Pop latest stash
4. Drop latest stash
7. [Tags](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/481)
1. Create tag...
2. Delete tag...
8. [Copy changes (Patch)](https://gitlab.com/gitlab-org/gitlab-web-ide/-/issues/475)
## Acceptance Criteria
* [ ] Newly supported source control operations are accessible via the Source Control panel under the "More Actions" menu

* [ ] Each newly supported source control operation should function as expected
* [ ] executed operation results in the expected source control change
* [ ] after an operation is performed the WebIDE reflects the updated repository state (without requiring a manual refresh)
* [ ] Where required/expected there should be clear real-time visual indicators that show progress such as loading, success, error, or others.
* [ ] If an operation fails, the user is shown a clear and actionable error message
## Implementation guide
Follow the VSCode's source control provider guide to implement the additional source control operations: https://code.visualstudio.com/api/extension-guides/scm-provider
epic