feat(tracemetrics): Add initial dataset implementation to dashboards

[narsaynorath]

This begins adding the traceMetrics dataset to Dashboards. This is still a WIP and different aspects of Metrics in dashboards still need iteration before being feature complete and releasable.

The functionality captured here are:

• The dataset button appears
• When selecting the dataset, the visualize bars load the first metric and selects it, as well as auto-selects the first applicable aggregate
• Users can add more metrics to compare
• Users can filter metrics
• Users can add a group by
• Users can save and edit a widget

The functionality that needs to be iterated on (i.e. not complete in this PR) are:

• Decide how to restrict when users can query different metrics (e.g. filters across different metrics can't be applied the same way we do other datasets)
• Group by should be restricted to the metrics selected
• Order by should be automatically selected and set to the aggregate
• Adding an alias needs to work
• Handle starting state/empty state better before we've loaded metrics
• Fix bug with new timeseries visualization
• Implement confidence footer

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: All tests successful. No failed tests found.

Additional details and impacted files

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