Modernize mapper core types

There's a number of best practices that have evolved in our use of
flat_maps and flat_sets since this code was originally written.

First, add std::less<> to the Compare template argument.  The default
for this is std::less<Key> which limits find() calls (and any lookup for
that matter) to only supporting std::string.  Using std::less<> allows
lookup by std::string_view, which can prevent some copies in some cases.

Next, add std::vector<...> to the types under the AllocatorOrContainer
template arg.  Per our coding standard, this overrides the default of
using boost::vector, and replaces it with std::vector, which, although
it has a very similar interface, tends to optimize better, and be better
supported overall.

The rest of this patch updates a couple places where the various types
were specifically hardcoded, so it moves to using the various using
declarations.

Tested: Unit tests;  Next patch tests this more fully.

Change-Id: I11e8ecb669f31193c55dda344b25d3fa5d191502
Signed-off-by: Ed Tanous <edtanous@google.com>
diff --git a/src/main.cpp b/src/main.cpp
index 86ef055..9ceb9ab 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -359,11 +359,9 @@
     }
 }
 
-void addObjectMapResult(
-    std::vector<InterfaceMapType::value_type>& objectMap,
-    const std::string& objectPath,
-    const std::pair<std::string, boost::container::flat_set<std::string>>&
-        interfaceMap)
+void addObjectMapResult(std::vector<InterfaceMapType::value_type>& objectMap,
+                        const std::string& objectPath,
+                        const ConnectionNames::value_type& interfaceMap)
 {
     // Adds an object path/service name/interface list entry to
     // the results of GetSubTree and GetAncestors.
@@ -494,13 +492,11 @@
     return ret;
 }
 
-boost::container::flat_map<std::string, boost::container::flat_set<std::string>>
-    getObject(const InterfaceMapType& interfaceMap, const std::string& path,
-              std::vector<std::string>& interfaces)
+ConnectionNames getObject(const InterfaceMapType& interfaceMap,
+                          const std::string& path,
+                          std::vector<std::string>& interfaces)
 {
-    boost::container::flat_map<std::string,
-                               boost::container::flat_set<std::string>>
-        results;
+    ConnectionNames results;
 
     // Interfaces need to be sorted for intersect to function
     std::sort(interfaces.begin(), interfaces.end());