Frontend - Metadata - Use custom properties in addition to plain properties

[Ark-kun]

Adapting to the recent TFX changes #2562 (comment)

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This change is 

[Bobgy]

The changes look good

[Bobgy]

Just want to double check, does the new UI work with current tfx sample?

[Bobgy]

/approve
/lgtm
/hold for backward compatibility confirmation, you can unhold once confirmed

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Bobgy

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[Bobgy]

Nevermind, I saw that you have always tried to use the old value first.
/hold cancel

[Ark-kun]

This is currently a backwards compatible change.
The old properties are still used (I've corrected the title), so the UX will still work with the current TFX sample.
Without this change, the UX will stop working for the TFX sample once the TFX SDK updates.
/hold cancel