[v2] test suite for v2 features

[yhwang]

/kind feature

Description:
Use this to trace the status of v2 features

Additional information:
Here is the KFP v2 project board:
https://github.com/orgs/kubeflow/projects/57/views/1

[yhwang]

• Exit handler: samples/core/exit_handler/exit_handler_v2.py
• Volume mount: samples/v2/pipeline_with_volume.py test(v2): use volume #1306
• Secret as Env: samples/v2/pipeline_with_secret_as_env.py test(v2): use secret as env #1296
• Secret as Volume: samples/v2/pipeline_with_secret_as_volume.py test(v2): secret as volume #1302
• Env support: samples/v2/pipeline_with_env.py test(v2): add env test case #1303
• Static loop: samples/core/loop_static/loop_static_v2.py test(v2): add end-2-end test case #1285
• Dynamic loop: samples/core/loop_parameter/loop_parameter_v2.py test(v2): add dynamic loop test case #1289