sdbusplus: use shorter type aliases

The sdbusplus headers provide shortened aliases for many types.
Switch to using them to provide better code clarity and shorter
lines.  Possible replacements are for:
  * bus_t
  * exception_t
  * manager_t
  * match_t
  * message_t
  * object_t
  * slot_t

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ibd2a0b512bfb7caf65bfab64b271d194da520aac
diff --git a/settings.hpp b/settings.hpp
index 5382fdd..1f96242 100644
--- a/settings.hpp
+++ b/settings.hpp
@@ -25,7 +25,7 @@
      * @param[in] filter - A vector of settings interfaces the caller is
      *            interested in.
      */
-    Objects(sdbusplus::bus::bus& bus, const std::vector<Interface>& filter);
+    Objects(sdbusplus::bus_t& bus, const std::vector<Interface>& filter);
     Objects(const Objects&) = default;
     Objects& operator=(const Objects&) = default;
     Objects(Objects&&) = delete;
@@ -47,7 +47,7 @@
     std::map<Interface, std::vector<Path>> map;
 
     /** @brief The Dbus bus object */
-    sdbusplus::bus::bus& bus;
+    sdbusplus::bus_t& bus;
 };
 
 namespace boot