[lldb][NFCI] Remove StructuredData::Dictionary::GetValueForKeyAsString overloads involving ConstString

[bulbazord]

Summary

In an effort to keep the ConstString StringPool small, I plan on
removing use of ConstString in StructuredData. The only class that
really uses it is StructuredData::Dictionary.

This one was fairly easy to remove, I plan on removing the others in
follow-up changes.

[mib]

I thought StructuredData::String used a ConstString for storage but it actually uses a std::string instead. Makes sense to remove this then. LGTM!

lldb/include/lldb/Utility/StructuredData.h

bool GetValueForKeyAsString(llvm::StringRef key, llvm::StringRef &result,
         if (default_val)
           result = default_val;
         else
           result = llvm::StringRef();
       }
       return success;
     }
 
-    bool GetValueForKeyAsString(llvm::StringRef key,
-                                ConstString &result) const {
-      ObjectSP value_sp = GetValueForKey(key);
-      if (value_sp.get()) {
-        if (auto string_value = value_sp->GetAsString()) {
-          result = ConstString(string_value->GetValue());
-          return true;
-        }
-      }
-      return false;
-    }
-
-    bool GetValueForKeyAsString(llvm::StringRef key, ConstString &result,
-                                const char *default_val) const {
-      bool success = GetValueForKeyAsString(key, result);
-      if (!success)
-        result.SetCString(default_val);
-      return success;
-    }
-
     bool GetValueForKeyAsDictionary(llvm::StringRef key,
                                     Dictionary *&result) const {
       result = nullptr;
       ObjectSP value_sp = GetValueForKey(key);
       if (value_sp.get()) {
         result = value_sp->GetAsDictionary();
         return (result != nullptr);
       }

lldb/source/Target/DynamicRegisterInfo.cpp

for (uint32_t i = 0; i < num_regs; ++i) {
     // { 'name':'rcx'       , 'bitsize' :  64, 'offset' :  16,
     // 'encoding':'uint' , 'format':'hex'         , 'set': 0, 'ehframe' : 2,
     // 'dwarf' : 2, 'generic':'arg4', 'alt-name':'arg4', },
     RegisterInfo reg_info;
     std::vector<uint32_t> value_regs;
     std::vector<uint32_t> invalidate_regs;
     memset(&reg_info, 0, sizeof(reg_info));
 
-    ConstString name_val;
-    ConstString alt_name_val;
-    if (!reg_info_dict->GetValueForKeyAsString("name", name_val, nullptr)) {
+    llvm::StringRef name_val;
+    if (!reg_info_dict->GetValueForKeyAsString("name", name_val)) {
       Clear();
       printf("error: registers must have valid names and offsets\n");
       reg_info_dict->DumpToStdout();
       return 0;
     }
-    reg_info.name = name_val.GetCString();
-    reg_info_dict->GetValueForKeyAsString("alt-name", alt_name_val, nullptr);
-    reg_info.alt_name = alt_name_val.GetCString();
+    reg_info.name = ConstString(name_val).GetCString();
+
+    llvm::StringRef alt_name_val;
+    if (reg_info_dict->GetValueForKeyAsString("alt-name", alt_name_val))
+      reg_info.alt_name = ConstString(alt_name_val).GetCString();
+    else
+      reg_info.alt_name = nullptr;
 
     llvm::Expected<uint32_t> byte_offset =
         ByteOffsetFromRegInfoDict(i, *reg_info_dict, byte_order);
     if (byte_offset)
       reg_info.byte_offset = byte_offset.get();
     else {
       LLDB_LOG_ERROR(log, byte_offset.takeError(),
                      "error while parsing register {1}: {0}", reg_info.name);