Resolve TSP type queries in files that aren't open (#4235)

[kinto0]

Summary:

TSP getComputedType (and getDeclaredType/getExpectedType) returned
null for any node in a file that wasn't open in the editor, even though
the file was on disk, reachable, and analyzed as a dependency of an open
file. Opening the same file made the identical (uri, range) query
succeed. This broke every node in Pyrefly's bundled stdlib stubs (e.g.
builtins.pyi), which clients like Pylance never didOpen.

Fixes #4228.

The root cause: computed_type_at_range and open_at_position built the
handle with make_open_handle, which always uses ModulePath::memory.
In-memory content only exists for opened files, so the memory-keyed handle
only matched open documents; closed files are keyed under FileSystem or
BundledTypeshed handles (whose SysInfo is inherited from the importer
and can't be reconstructed here), so the lookup missed and short-circuited
to null.

New helper query_transaction_and_handle resolves a path to the handle the
checker actually analyzes it under:

• open files -> in-memory overlay (unchanged fast path);
• otherwise reuse the already-loaded handle: the filesystem handle when it
  can be rebuilt directly, else a by-path scan that reuses the loaded
  BundledTypeshed handle so stdlib queries don't re-check typeshed;
• fall back to a fresh filesystem handle read from disk when the file
  hasn't been analyzed yet.

It then forces a full solve at Require::Everything, the only level that
retains bindings/answers — exactly the data the type lookup reads — so the
result is available regardless of what require level the file was loaded
at as a dependency. Open-file queries are unchanged; only the previously
null closed-file path does additional work, and bundled typeshed reuses
its already-solved handle.

Differential Revision: D113135763

[meta-codesync]

@kinto0 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D113135763.

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[stroxler]

Review automatically exported from Phabricator review in Meta.