[WIP] Supporting hyperparameter tuining on custom training job task

[bnsblue]

TL;DR

Please replace this text with a description of what this PR accomplishes.

Type

• Bug Fix
• Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

How did you fix the bug, make the feature etc. Link to any design docs etc

Tracking Issue

https://github.com/lyft/flyte/issues/

Follow-up issue

NA
OR
https://github.com/lyft/flyte/issues/

[codecov-io]

Codecov Report

Merging #137 into master will increase coverage by 0.29%.
The diff coverage is 85.13%.

@@            Coverage Diff             @@
##           master     #137      +/-   ##
==========================================
+ Coverage   61.39%   61.69%   +0.29%     
==========================================
  Files         106      106              
  Lines        5997     6064      +67     
==========================================
+ Hits         3682     3741      +59     
- Misses       1939     1943       +4     
- Partials      376      380       +4     

Impacted Files	Coverage Δ
...sks/plugins/k8s/sagemaker/hyperparameter_tuning.go	62.82% <74.64%> (+1.33%)	⬆️
...o/tasks/plugins/k8s/sagemaker/plugin_test_utils.go	94.57% <93.93%> (-0.58%)	⬇️
go/tasks/plugins/k8s/sagemaker/utils.go	69.08% <100.00%> (+1.08%)	⬆️

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[eapolinario]

Moved to flyteorg/flyte#4120