Added previous metric date and value to metrics controller for comparisons/trends

[briankalwat]

Proposed Changes

This change simply surfaces the value and date of the previous metric value to the lava of the liquid dashboard widget, for determining comparisons.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality, which has been approved by the core team)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

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