Migrate to a common timer class

This change pulls in sdeventplus and uses the timer implementation as
a drop in for the currently included timer.

Tested:
    Unit tests still build but are not currently running. Manually
    tested this change on a zaius machine and made sure timers went off.

Change-Id: I2808196581fc766843931403b83fead16926b0ae
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/Makefile.am b/Makefile.am
index a3fd0d6..fa3f92b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -18,7 +18,6 @@
 		dhcp_configuration.hpp \
 		vlan_interface.hpp \
 		rtnetlink_server.hpp \
-		timer.hpp \
 		dns_updater.hpp \
 		watch.hpp \
 		argument.hpp
@@ -52,7 +51,6 @@
 		dhcp_configuration.cpp \
 		vlan_interface.cpp \
 		rtnetlink_server.cpp \
-		timer.cpp \
 		dns_updater.cpp \
 		watch.cpp
 
@@ -71,6 +69,7 @@
 phosphor_network_manager_LDFLAGS = \
 		$(SYSTEMD_LIBS) \
 		$(SDBUSPLUS_LIBS) \
+		$(SDEVENTPLUS_LIBS) \
 		$(PHOSPHOR_DBUS_INTERFACES_LIBS) \
 		$(PHOSPHOR_LOGGING_LIBS) \
 		-lstdc++fs
@@ -78,6 +77,7 @@
 phosphor_network_manager_CXXFLAGS = \
 		$(SYSTEMD_CFLAGS) \
 		$(SDBUSPLUS_CFLAGS) \
+		$(SDEVENTPLUS_CFLAGS) \
 		$(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
 		$(PHOSPHOR_LOGGING_CFLAGS) \
 		-flto