Revert "Centralize the handling of completion for simple argument lists. (#82085)"

This reverts commit 21631494b068d9364b8dc8f18e59adee9131a0a5.

Reverted because of greendragon failure:

******************** TEST 'lldb-api :: functionalities/completion/TestCompletion.py' FAILED ********************
Script:

1 files changed, 8 insertions, 0 deletions

diff --git a/lldb/source/Commands/CommandObjectSettings.cpp b/lldb/source/Commands/CommandObjectSettings.cpp
index 0cf3d1d..5fb7dcc 100644
--- a/lldb/source/Commands/CommandObjectSettings.cpp
+++ b/lldb/source/Commands/CommandObjectSettings.cpp
@@ -262,6 +262,14 @@ public:
 
   ~CommandObjectSettingsShow() override = default;
 
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
+    lldb_private::CommandCompletions::InvokeCommonCompletionCallbacks(
+        GetCommandInterpreter(), lldb::eSettingsNameCompletion, request,
+        nullptr);
+  }
+
 protected:
   void DoExecute(Args &args, CommandReturnObject &result) override {
     result.SetStatus(eReturnStatusSuccessFinishResult);