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/dbus_interface.cpp b/src/entity_manager/dbus_interface.cpp
index d7169ce..e42d9cd 100644
--- a/src/entity_manager/dbus_interface.cpp
+++ b/src/entity_manager/dbus_interface.cpp
@@ -3,9 +3,9 @@
 #include "perform_probe.hpp"
 #include "utils.hpp"
 
-#include <boost/container/flat_map.hpp>
 #include <phosphor-logging/lg2.hpp>
 
+#include <flat_map>
 #include <fstream>
 #include <regex>
 #include <string>
@@ -249,7 +249,7 @@
         "AddObject",
         [&systemConfiguration, jsonPointerPath{std::string(jsonPointerPath)},
          path{std::string(path)}, board,
-         this](const boost::container::flat_map<std::string, JsonVariantType>&
+         this](const std::flat_map<std::string, JsonVariantType, std::less<>>&
                    data) {
             nlohmann::json::json_pointer ptr(jsonPointerPath);
             nlohmann::json& base = systemConfiguration[ptr];