feat(experiment_status): Add trial name

[gaocegege]

Signed-off-by: Ce Gao gaoce@caicloud.io

What this PR does / why we need it:

This PR added a new field in v1alpha3 Exepriment status, which stores the best trial name.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

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This change is 

[gaocegege]

/assign @johnugeorge @hougangliu

[hougangliu]

/lgtm
BTW, for observation field, now we only show objective metric and "best" value. in fact, we can add "min", "max", "latest" value for more information like other platform (such as ray), WDYT?

[gaocegege]

We show metrics and parameter assignments. I am not sure if I get your idea. Could you please explain more?

[hougangliu]

We show metrics and parameter assignments. I am not sure if I get your idea. Could you please explain more?

for example, for now if objective metrics is loss, in experiment or trial status, it show the best loss metrics minimum value like below:

observation:
  metrics:
    - name: loss
       value: 0.0001

we can detail it more for a better viewpoint like ray:

observation:
 metrics:
   - name: loss
     min: 0.0001
     max: 0.1234
     latest: 0.1111

[gaocegege]

Gotcha. SGTM

[hougangliu]

Gotcha. SGTM

/approve
We can enhance it in other PR

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