[mlir] Add window.workDoneProgress LSP capability (llvm#143449)

Adds the capability flag for [server-initiated work-done
progress](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#serverInitiatedProgress).

Author: AmaranthineCodices

mlir/include/mlir/Tools/lsp-server-support/Protocol.h

@@ -158,6 +158,12 @@ struct ClientCapabilities {
   /// Client supports CodeAction return value for textDocument/codeAction.
   /// textDocument.codeAction.codeActionLiteralSupport.
   bool codeActionStructure = false;
+
+  /// Client supports server-initiated progress via the
+  /// window/workDoneProgress/create method.
+  ///
+  /// window.workDoneProgress
+  bool workDoneProgress = false;
 };
 
 /// Add support for JSON serialization.

mlir/lib/Tools/lsp-server-support/Protocol.cpp

@@ -289,6 +289,11 @@ bool mlir::lsp::fromJSON(const llvm::json::Value &value,
       if (codeAction->getObject("codeActionLiteralSupport"))
         result.codeActionStructure = true;
     }
+    if (auto *window = textDocument->getObject("window")) {
+      if (std::optional<bool> workDoneProgressSupport =
+              window->getBoolean("workDoneProgress"))
+        result.workDoneProgress = *workDoneProgressSupport;
+    }
   }
   return true;
 }