[lldb] Add tests for setting completions and enable 'settings remove' completion

llvm-svn: 369521
diff --git a/lldb/source/Commands/CommandObjectSettings.cpp b/lldb/source/Commands/CommandObjectSettings.cpp
index d756e03..200ef34 100644
--- a/lldb/source/Commands/CommandObjectSettings.cpp
+++ b/lldb/source/Commands/CommandObjectSettings.cpp
@@ -613,6 +613,8 @@
 
   ~CommandObjectSettingsRemove() override = default;
 
+  bool WantsCompletion() override { return true; }
+
   int HandleArgumentCompletion(
       CompletionRequest &request,
       OptionElementVector &opt_element_vector) override {