Revert "[lldb][Format] Make function name frame-format variables work without debug-info" (#137757)

Reverts llvm/llvm-project#137408

This change broke `lldb/test/Shell/Unwind/split-machine-functions.test`.

The test binary has a symbol named `_Z3foov.cold` and the test expects
the backtrace to print the name of the cold part of the function like
this:

```
# SPLIT: frame #1: {{.*}}`foo() (.cold) +
```
but now it gets

```
frame #1: 0x000055555555514f split-machine-functions.test.tmp`foo() + 12
```

1 files changed, 2 insertions, 36 deletions

diff --git a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
index ab8e9883..283e867 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp
@@ -381,34 +381,6 @@ GetDemangledScope(const SymbolContext &sc) {
   return demangled_name.slice(info->ScopeRange.first, info->ScopeRange.second);
 }
 
-static bool PrintDemangledArgumentList(Stream &s, const SymbolContext &sc) {
-  assert(sc.symbol);
-
-  Mangled mangled = sc.GetPossiblyInlinedFunctionName();
-  if (!mangled)
-    return false;
-
-  auto demangled_name = mangled.GetDemangledName().GetStringRef();
-  if (demangled_name.empty())
-    return false;
-
-  const std::optional<DemangledNameInfo> &info = mangled.GetDemangledInfo();
-  if (!info)
-    return false;
-
-  // Function without a basename is nonsense.
-  if (!info->hasBasename())
-    return false;
-
-  if (info->ArgumentsRange.second < info->ArgumentsRange.first)
-    return false;
-
-  s << demangled_name.slice(info->ArgumentsRange.first,
-                            info->ArgumentsRange.second);
-
-  return true;
-}
-
 bool CPlusPlusLanguage::CxxMethodName::TrySimplifiedParse() {
   // This method tries to parse simple method definitions which are presumably
   // most comman in user programs. Definitions that can be parsed by this
@@ -1918,6 +1890,8 @@ bool CPlusPlusLanguage::GetFunctionDisplayName(
 bool CPlusPlusLanguage::HandleFrameFormatVariable(
     const SymbolContext &sc, const ExecutionContext *exe_ctx,
     FormatEntity::Entry::Type type, Stream &s) {
+  assert(sc.function);
+
   switch (type) {
   case FormatEntity::Entry::Type::FunctionScope: {
     std::optional<llvm::StringRef> scope = GetDemangledScope(sc);
@@ -1951,14 +1925,6 @@ bool CPlusPlusLanguage::HandleFrameFormatVariable(
   }
 
   case FormatEntity::Entry::Type::FunctionFormattedArguments: {
-    // This ensures we print the arguments even when no debug-info is available.
-    //
-    // FIXME: we should have a Entry::Type::FunctionArguments and
-    // use it in the plugin.cplusplus.display.function-name-format
-    // once we have a "fallback operator" in the frame-format language.
-    if (!sc.function && sc.symbol)
-      return PrintDemangledArgumentList(s, sc);
-
     VariableList args;
     if (auto variable_list_sp = GetFunctionVariableList(sc))
       variable_list_sp->AppendVariablesWithScope(eValueTypeVariableArgument,