LSP: confusing type in WorkspaceEdit breaks JSON serialization

There is a type that confuses the JSON serialization in WorkspaceEdit, and it is:

std::optional<std::variant<QList<TextDocumentEdit>,                         QList<std::variant<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>>>

Basically, if you deserialize a WorkspaceEdit with a

QList<std::variant<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>

and then later reserialize it, you will obtain a QList<TextDocumentEdit> with invalid content.

This was found while writing tests for renaming qml components and their corresponding files.