Support multiple metric logs in one line

[hougangliu]

for now, in one line, only $metricsName=$value (without blank) can be parsed.
By this PR, blank can be tolerant before and after "="; Also in the same line, multiple metrics couple can be parsed

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This change is 

[hougangliu]

/cc @gaocegege @johnugeorge

[gaocegege]

Can we add some unit test cases for the change?

[hougangliu]

Can we add some unit test cases for the change?

Sure, I can update it soon

[gaocegege]

Thanks. I cannot confirm the effect of the code by code review, thus prefer having such test cases to illustrate it.

[hougangliu]

Thanks. I cannot confirm the effect of the code by code review, thus prefer having such test cases to illustrate it.

I had updated image in examples/v1alpha3/file-metricscollector-example.yaml to test the change

[hougangliu]

/test kubeflow-katib-presubmit

[hougangliu]

/test kubeflow-katib-presubmit

[johnugeorge]

Can we document this now? There will be more similar things in the future

[hougangliu]

Can we document this now? There will be more similar things in the future

I will implement filter filed in coming days and then will document how filter should be defined and what default filter is.

[gaocegege]

/lgtm

[johnugeorge]

/approve

[k8s-ci-robot]

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