Change sample test to read test arguments from yaml config file

[numerology]

Part of #1750
Now the params used for each sample test live in test/sample-test/configs dir. If no config file is provided, default param values will be used. Also, common constants used in sample test infra are moved into a dedicated python file.

Moving image injection and into config files guideline of adding a sample test will be in following PRs.

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This change is 

[gaoning777]

Could we add a readme to explain the steps to add a sample test?

[numerology]

Could we add a readme to explain the steps to add a sample test?

Sure thing. Will do that in another PR.

[Ark-kun]

/lgtm

[gaoning777]

Could we add a readme to explain the steps to add a sample test?

Sure thing. Will do that in another PR.

If not the readme, could you provide the spec about the config yaml in this PR? I think this should be a minimal work such as

testname:
    type: string
    required: true
test_timeout:
    type: float
    required: false
arguments:
    type: object
    required: false

This will be important because users need to know what the sample test infra is expecting from the configuration.
WDYT?

[numerology]

Could we add a readme to explain the steps to add a sample test?

Sure thing. Will do that in another PR.

If not the readme, could you provide the spec about the config yaml in this PR? I think this should be a minimal work such as

testname:
    type: string
    required: true
test_timeout:
    type: float
    required: false
arguments:
    type: object
    required: false

This will be important because users need to know what the sample test infra is expecting from the configuration.
WDYT?

Just to confirm. Are you talking about add this spec in a separated file, or inline in the comment in the config.yaml itself?

[Ark-kun]

/lgtm

[gaoning777]

/lgtm

[numerology]

/test kubeflow-pipeline-sample-test

[numerology]

/approve

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