This PR adds support for server-sided `RpcRef` reuse and fixes a bug
where trace nodes in the InfoView would close while the file was still
being processed.
The core of the trace node issue is that the server always serves new
RPC references in every single response to the client, which means that
the client is forced to reset its UI state.
In a previous attempt at fixing this (#8056), the server would memorize
the RPC-encoded JSON of interactive diagnostics (which includes RPC
references) and serve it for as long as it could reuse the snapshot
containing the diagnostics, so that RPC references are reused. The
problem with this was that the client then had multiple finalizers
registered for the same RPC reference (one for every reused RPC
reference that was served), and once the first reference was
garbage-collected, all other reused references would point into the
void.
This PR takes a different approach to resolve the issue: The meaning of
`$/lean/rpc/release` is relaxed from "Free the object pointed to by this
RPC reference" to "Decrement the RPC reference count of the object
pointed to by this RPC reference", and the server now maintains a
reference count to track how often a given `RpcRef` was served. Only
when every single served instance of the `RpcRef` has been released, the
object is freed. Additionally, the reuse mechanism is generalized from
being only supported for interactive diagnostics, to being supported for
any object using `WithRpcRef`. In order to make use of reusable RPC
references, downstream users still need to memorize the `WithRpcRef`
instances accordingly.
Closes#8053.
### Breaking changes
Since `WithRpcRef` is now capable of tracking its identity to decide
which `WithRpcRef` usage constitutes a reuse, the constructor of
`WithRpcRef` has been made `private` to discourage downstream users from
creating `WithRpcRef` instances with manually-set `id`s. Instead,
`WithRpcRef.mk` (which lives in `BaseIO`) is now the preferred way to
create `WithRpcRef` instances.
