EntityManager: Make MapperGetSubTreeResponse type comprehensible

From there, rework a bunch of uses of the unaliased types to use the new
aliased types and fix up some of the variable names to improve
readability.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I498e0d93091cae43e59907ee1908afc97ac601ee
diff --git a/include/EntityManager.hpp b/include/EntityManager.hpp
index eb8a86d..2b4565b 100644
--- a/include/EntityManager.hpp
+++ b/include/EntityManager.hpp
@@ -30,16 +30,8 @@
 #include <optional>
 #include <string>
 
-// paths - > interfaces -> properties
-using MapperGetSubTreeResponse = boost::container::flat_map<
-    std::string,
-    boost::container::flat_map<
-        std::string,
-        boost::container::flat_map<std::string, DBusValueVariant>>>;
-
-// vector of tuple<map<propertyName, variant>, D-Bus path>>
-using FoundDeviceT = std::vector<std::tuple<
-    boost::container::flat_map<std::string, DBusValueVariant>, std::string>>;
+// The string is the path to the object hosting the interface
+using FoundDeviceT = std::vector<std::tuple<DBusInterface, std::string>>;
 
 struct CmpStr
 {