Add GetTaskMetrics and GetTaskLogs to agent

[pingsutw]

Tracking issue

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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b96419c) 58.12% compared to head (50b6ba0) 58.16%.
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4662      +/-   ##
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+ Coverage   58.12%   58.16%   +0.03%     
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  Files         626      626              
  Lines       53815    53786      -29     
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+ Hits        31278    31282       +4     
+ Misses      20035    19998      -37     
- Partials     2502     2506       +4     

Flag	Coverage Δ
unittests	58.16% <ø> (+0.03%)	⬆️

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[andrewwdye]

It will be challenging to anticipate or keep up with all possible metrics (and aggregations). I suspect at minimum we will want some string escape hatch, i.e., oneof {enum string}, if not just a string encoding the query (metric + aggregation)

[andrewwdye]

One minor comment on token, but otherwise looks good

[honnix]

Thank you for working on this feature. A couple of questions:

Where are these used? What is the different between log links returned by the endpoint and those propagated via Resource?