Flat map all the things

In an earlier commit, entity-manager gained required dependency
on std::flat_map.  This means that EM can only compile with gcc-15,
which the project only recently moved to.  Rather than move backwards,
port forward all uses of boost flat_map and flat_set to their std
equivalents.

Tested: entity-manager launches and enumerates devices on
gb200-obmc.

Change-Id: Id24803057711c60d5b00f436db80b27edbb756a3
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/src/entity_manager/utils.hpp b/src/entity_manager/utils.hpp
index 04aa992..a8bba16 100644
--- a/src/entity_manager/utils.hpp
+++ b/src/entity_manager/utils.hpp
@@ -1,15 +1,16 @@
 #pragma once
 
 #include <boost/asio/io_context.hpp>
-#include <boost/container/flat_map.hpp>
 #include <nlohmann/json.hpp>
 #include <sdbusplus/asio/connection.hpp>
 
+#include <flat_map>
+
 using DBusValueVariant =
     std::variant<std::string, int64_t, uint64_t, double, int32_t, uint32_t,
                  int16_t, uint16_t, uint8_t, bool, std::vector<uint8_t>>;
-using DBusInterface = boost::container::flat_map<std::string, DBusValueVariant>;
-using DBusObject = boost::container::flat_map<std::string, DBusInterface>;
+using DBusInterface = std::flat_map<std::string, DBusValueVariant, std::less<>>;
+using DBusObject = std::flat_map<std::string, DBusInterface, std::less<>>;
 
 constexpr const char* configurationOutDir = "/var/configuration/";
 constexpr const char* versionHashFile = "/var/configuration/version";