fix: make AsyncDataTree.hasNode check inner tree consistency (fixes #316443) (#316450)

The hasNode method only checked the async data tree's own nodes map,
but isCollapsed goes through the inner compressed tree model which has
its own node map. When these maps are temporarily out of sync during
a tree refresh, hasNode returns true but isCollapsed throws a TreeError.

Fix by also verifying the inner tree has the element, preventing
callers from proceeding with operations on nodes the inner tree
doesn't know about.

Co-authored-by: vs-code-engineering[bot] <122617954+vs-code-engineering[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>