Deal with new lint rule strict_top_level_inference

[gkc]

Describe the bug

This new lint rule generates 60-ish lint info messages in at_secondary_server between lib and test. I started to resolve it during some other work, but it is a large cascade of busywork some of which could actually be dangerous so for now I'm going to add strict_top_level_inference: false to analysis_options.yaml. This ticket is a reminder to deal with this later.

Steps to reproduce

dart analyze in at_secondary_server

Expected behavior

No lint when strict_top_level_inference is set to true