Enforce strict-raw-types

[srawlins]

Enabling strict-raw-types leads to changes in a few categories:

• use var for inference
• put a type on a raw Future
• put a bound on a type parameter like Object
• put types on a raw Map. Cringe. This one doesn't look pretty, but can be helped once we migrate to null safety with the use of non-function type aliases.

[jcollins-g]

Looks good, yeah, I'm not a fan of the explicit Object everywhere but I like how strict-raw-types seems to eliminate the ambiguity about what is derived vs implicit dynamic.

[jcollins-g]

This probably should be added to analysis_options_presubmit.yaml?

[srawlins]

Done.

[srawlins]

Yeah T extends Object definitely makes my head scratch, for now. It looks like it is indicating some important grand distinction, when really it's just to avoid dynamic. I hope it just becomes more familiar.