bug: UpsertTemplateUsageStats creates lots of DB load

[spikecurtis]

In our dogfood deployment over 5 days in early June:

Avg Execution Time: 552ms
Num Times called: 1.8k
Avg Rows: 4

https://www.notion.so/coderhq/UpsertTemplateUsageStats-209d579be59280a68bbff80081a92b93?source=copy_link