[explore] Tweaks to sorting in metric search

[zuzana-vej]

Is your feature request related to a problem? Please describe.
Currently when users searches metric in Chart Explore Metric dropdown, the search first displays the "ending" string of the metric, even if there is an exact match. For example if you search for san_francisco and your metrics include population_in_san_francisco san_francisco and san_francisco_weather your first result would be population_in_san_francisco

The proposal is to at least put the exact match first. See below more on ideal experience.

Describe the solution you'd like

Ideal experience?

1. exact match
2. starting string matches
3. anything else (string in middle or end)

From above example the expected result would be
san_francisco
san_francisco_weather
population_in_san_francisco

[junlincc]

@zuzana-vej thanks for suggesting! it makes perfect sense. It is a good-first-issue, but in case no one picks it up, we should be able to squeeze it in when enhancing the metric component.