SYNC-5167: Errors only dashboards

[bendk]

My hope for the sync dashboard was that it could combine errors + sync metrics + other glean metrics. However, the latter 2 parts are performing poorly and we are currently only collecting metrics on Android. This updates the SYNC dashboard to only show the things that are actually working: Android errors.

The resulting dashboard is pretty functional, although somewhat bare: https://yardstick.mozilla.org/d/sync-main/sync

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[bendk]

I talked with the data team last week and now I'm thinking we might be able to optimize these queries sooner than later. I'm going to close this one for now, maybe it's not needed.