Implement configure_runner, configure_metric

[mpolson64]

Summary: configure_runner and configure_metric allow users to attach custom Runners and Metrics to their experiment.

configure_runner is fairly straightforward and just sets experiment.runner

configure_metric is more complicated: given a list of IMetrics it iterates through and tries to find a metric with the same name somewhere on the experiment. In order it checks the Objective (single, MOO, or secularized), outcome constraints, then tracking metrics. If no metric with a matching name is found then the provided metric is added as a tracking metric.

Differential Revision: D66305614

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D66305614

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.96021% with 19 lines in your changes missing coverage. Please review.

Project coverage is 95.77%. Comparing base (4aa1d65) to head (c7b8aeb).

Files with missing lines	Patch %	Lines
ax/preview/api/client.py	81.81%	12 Missing :warning:
ax/preview/api/utils/instantiation/from_string.py	94.11%	4 Missing :warning:
ax/preview/api/utils/instantiation/from_config.py	94.23%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3104 +/- ## ========================================== + Coverage 95.43% 95.77% +0.33% ========================================== Files 495 500 +5 Lines 49956 50316 +360 ========================================== + Hits 47674 48188 +514 + Misses 2282 2128 -154 ```

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