bug: GetLatestWorkspaceBuilds creates lots of DB load

[spikecurtis]

In our dogfood deployment over 5 days in early June:

Avg Execution Time: 349.5ms
Num Times Called: 25805
Avg Rows: 4677

https://www.notion.so/coderhq/GetLatestWorkspaceBuilds-209d579be5928025a686ec5a4a2defd2?source=copy_link