This is another pure refactor, to prepare for adding direct WSL support.
### Todo
* [x] Represent `paths` in the same way for all workspaces, instead of
having a completely separate SSH representation
* [x] Adjust sqlite tables
* [x] `ssh_projects` -> `ssh_connections` (drop paths)
* [x] `workspaces.local_paths` -> `paths`
* [x] remove duplicate path columns on `workspaces`
* [x] Add migrations for backward-compatibility
Release Notes:
- N/A
---------
Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>
While working on implementing `add_recent_documents` for Windows, I
found that the process is significantly more complex compared to macOS.
On macOS, simply registering the `add_recent_documents` function is
enough, as the system handles everything automatically.
On Windows, however, there are two cases to consider:
- **Files opened by the app**: These appear in the "Recent" section (as
shown in the screenshot, "test.txt") and are managed automatically by
Windows (by setting windows registry), similar to macOS.

- **Folders opened by the app**: This is more complicated because
Windows does not handle it automatically, requiring the application to
track opened folders manually.
To address this, this PR introduces a `History Manager` along with
`HistoryManagerEvent::Update` and `HistoryManagerEvent::Delete` events
to simplify the process of managing recently opened folders.
https://github.com/user-attachments/assets/a2581c15-7653-4faf-96b0-7c48ab1dcc8d
Release Notes:
- N/A
---------
Co-authored-by: Mikayla Maki <mikayla@zed.dev>