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/entity_manager.hpp b/src/entity_manager/entity_manager.hpp
index c21b94e..70f7a4f 100644
--- a/src/entity_manager/entity_manager.hpp
+++ b/src/entity_manager/entity_manager.hpp
@@ -8,11 +8,11 @@
 #include "power_status_monitor.hpp"
 #include "topology.hpp"
 
-#include <boost/container/flat_map.hpp>
 #include <nlohmann/json.hpp>
 #include <sdbusplus/asio/connection.hpp>
 #include <sdbusplus/asio/object_server.hpp>
 
+#include <flat_map>
 #include <string>
 
 class EntityManager
@@ -84,7 +84,7 @@
     boost::asio::steady_timer propertiesChangedTimer;
     size_t propertiesChangedInstance = 0;
 
-    boost::container::flat_map<std::string, sdbusplus::bus::match_t>
+    std::flat_map<std::string, sdbusplus::bus::match_t, std::less<>>
         dbusMatches;
 
     void startRemovedTimer(boost::asio::steady_timer& timer,