tests: move "venv" to "build-root" directory from "test" directory

Type: refactor

- refactored VPP test code to remove "ignore_path" variable
  from "discover_tests" function and "run_test" code
- configured VPP test makefile, config file, and 'run.sh' shell script
  to move "venv" directory from "test" dir to "build-root" dir

Signed-off-by: Saima Yunus <yunus.saima.234@gmail.com>
Change-Id: Id2beecbb99f24ce13ed118a1869c5adbef247e50

.gitignore

@@ -18,10 +18,10 @@
 /build-root/rpmbuild/
 /build-root/test-doc/
 /build-root/test-cov/
+/build-root/test/
 /test/run/
 /test/build/
 /test/coverage/
-/test/venv/
 /test/vapi_test/
 /test/doc/build/
 /build-config.mk