Fixing time table viz for adhoc metrics

[michellethomas]

The time table viz is broken for adhoc metrics. In the time table viz MetricOption is passed metric information that was gathered from slice.datasource.metrics, but AdhocMetrics aren't in that list so it errors. We can pass through the metric if it's already an object.

MetricOption in this case is just being used to display the metric name or verbose name with a link from a given url. So it's not a problem that metrics from the database are structured differently from AdhocMetrics, the label/name/verbose name is the only necessary prop.

@GabeLoins @mistercrunch @graceguo-supercat

[mistercrunch]

LGTM

[codecov-io]

Codecov Report

Merging #5117 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5117   +/-   ##
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  Coverage   77.52%   77.52%           
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  Files          44       44           
  Lines        8728     8728           
=======================================
  Hits         6766     6766           
  Misses       1962     1962

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