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.cpp b/settings.cpp
index 2fa2511..778dbd8 100644
--- a/settings.cpp
+++ b/settings.cpp
@@ -16,8 +16,7 @@
 constexpr auto mapperPath = "/xyz/openbmc_project/object_mapper";
 constexpr auto mapperIntf = "xyz.openbmc_project.ObjectMapper";
 
-Objects::Objects(sdbusplus::bus::bus& bus,
-                 const std::vector<Interface>& filter) :
+Objects::Objects(sdbusplus::bus_t& bus, const std::vector<Interface>& filter) :
     bus(bus)
 {
     auto depth = 0;