cleanup: move EM service code in EM directory

Improving repository structure increases maintainability.

Change-Id: I7f746a5d491dda256a06143f516e7d078a761c14
Signed-off-by: Christopher Meis <christopher.meis@9elements.com>
diff --git a/meson.build b/meson.build
index cc5a78e..290b5c0 100644
--- a/meson.build
+++ b/meson.build
@@ -170,7 +170,7 @@
         executable(
             'test_topology',
             'test/test_topology.cpp',
-            'src/topology.cpp',
+            'src/entity_manager/topology.cpp',
             cpp_args: test_boost_args,
             dependencies: [
                 gtest,