This PR addresses the post-merge review comments from
https://github.com/astral-sh/ruff/pull/19041, specifically it:
- Rename `WorkspaceSnapshot` to `SessionSnapshot`
- Rename `take_workspace_snapshot` to `take_session_snapshot`
- Rename `take_snapshot` to `take_document_snapshot`
- Move `AssertUnwindSafe` closer to the `catch_unwind` call which
requires the assertion
## Summary
This PR adds a new trait to support running a request in the background.
Currently, there exists a `BackgroundDocumentRequestHandler` trait which
is similar but is scoped to a specific document (file in an editor
context). The new trait `BackgroundRequestHandler` is not tied to a
specific document nor a specific project but it's for the entire
workspace.
This is added to support running workspace wide requests like computing
the [workspace
diagnostics](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_diagnostic)
or [workspace
symbols](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_symbol).
**Note:** There's a slight difference with what a "workspace" means
between the server and ty. Currently, there's a 1-1 relationship between
a workspace in an editor and the project database corresponding to that
workspace in ty but this could change in the future when Micha adds
support for multiple workspaces or multi-root workspaces.
The data that would be required by the request handler (based on
implementing workspace diagnostics) is the list of databases
(`ProjectDatabse`) corresponding to the projects in the workspace and
the index (`Index`) that contains the open documents. The
`WorkspaceSnapshot` represents this and is passed to the handler similar
to `DocumentSnapshot`.
## Test Plan
This is used in implementing the workspace diagnostics which is where
this is tested.
Micha Reiser
Dhruv Manilawala
Charlie Marsh