Misc: Remove StringUtil::{Starts,Ends}With, use C++20

src/core/gdb_protocol.cpp

@@ -306,7 +306,7 @@ std::string ProcessPacket(const std::string_view& data)
   // Try to invoke packet command.
   bool processed = false;
   for (const auto& command : COMMANDS) {
-    if (StringUtil::StartsWith(packet->data(), command.first)) {
+    if (packet->starts_with(command.first)) {
       Log_DebugPrintf("Processing command '%s'", command.first);
 
       // Invoke command, remove command name from payload.

src/core/memory_card_image.cpp

@@ -775,7 +775,7 @@ bool MemoryCardImage::ImportSave(DataArray* data, const char* filename)
     return false;
   }
 
-  if (StringUtil::EndsWith(filename, ".mcs"))
+  if (std::string_view(filename).ends_with(".mcs"))
   {
     return ImportSaveWithDirectoryFrame(data, filename, sd);
   }

src/core/pcdrv.cpp

@@ -82,7 +82,7 @@ static std::string ResolveHostPath(const std::string& path)
   const std::string& root = g_settings.pcdrv_root;
   std::string canonicalized_path = Path::Canonicalize(Path::Combine(root, path));
   if (canonicalized_path.length() < root.length() ||                      // Length has to be longer (a file),
-      !StringUtil::StartsWith(canonicalized_path, root) ||                // and start with the host root,
+      !canonicalized_path.starts_with(root) ||                            // and start with the host root,
       canonicalized_path[root.length()] != FS_OSPATH_SEPARATOR_CHARACTER) // and we can't access a sibling.
   {
     Log_ErrorPrintf("Denying access to path outside of PCDrv directory. Requested path: '%s', "