Pipeline unit tests create two artifacts in source directories

[kevin-bates]

Whenever I run server-side pipeline tests (e.g., pytest -v elyra/tests/pipeline) there are two artifacts produced that make it annoying when trying to check in and commit changes. Following the tests, a git status command will produce the following:

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	elyra/tests/pipeline/resources/test_pipelines/kfp/kfp-multi-node-generic.yaml
	elyra/tests/pipeline/resources/test_pipelines/kfp/kfp-one-node-generic.yaml

These files must first be cleared before their accidental inclusion into git.

If these are necessary to validate functionality, the test should make appropriate use of temporary directories so that these do not appear within the population of source-controlled files.

[ptitzler]

I'll take a look. These are code gen test artifacts.