Remove epc.py and use from python files

All core networks have been migrated to a file-based configuration.
References to epc.py are not needed anymore. Remove all unused XML
steps.

ci-scripts/tests/test-runner/run.sh

@@ -30,11 +30,6 @@ python3 main.py \
   --UEUserName=NONE \
   --UEPassword=NONE \
   --UESourceCodePath=NONE \
-  --EPCIPAddress=localhost \
-  --EPCType=OAI \
-  --EPCUserName=NONE \
-  --EPCPassword=NONE \
-  --EPCSourceCodePath=NONE \
   --XMLTestFile=tests/test-runner/test.xml
 
 python3 main.py \