Eliminate LspTestWorkspace #82917
Description
LSP tests are creating two workspaces with WorkspaceKind.Host: LspTestWorkspace and LanguageServerWorkspace. This breaks invariant that there can only be a single Host workspace.
LspTestWorkspace needs to be eliminated -- test tests should work directly with LanguageServerWorkspace
Tracks workaround in PdbMatchingSourceTextProvider: #82905