[wpiutil] Replace LLVM StringMap impl with std::map

As string_view operations on std::map<std::string> won't be integrated
until C++26, placeholder implementations are used which are less efficient
in a couple of situations (e.g. insert with hint).

sysid/src/main/native/cpp/view/LogLoader.cpp

@@ -16,6 +16,7 @@
 #include <imgui.h>
 #include <imgui_stdlib.h>
 #include <portable-file-dialogs.h>
+#include <wpi/SmallVector.h>
 #include <wpi/SpanExtras.h>
 #include <wpi/StringExtras.h>
 #include <wpi/fs.h>