enable strict-inference

[devoncarew]

Similar to #125, this is a proposal to enable strict-inference in the recommended lint set. We'd have to believe this is the way we want to recommend that people write Dart code.

See #151 for the related strict-raw-types flag.

[devoncarew]

From a discussion with @leafpetersen, he considered this a clear win - adding it would provide value to users w/o any real downsides.

[devoncarew]

For posterity, from https://dart.dev/tools/analysis#enabling-additional-type-checks:

Directs the type inference engine to never chooses the dynamic type when it can’t determine a static type.

final lines = {}; // Inference failure

[lrhn]

This is a good stepping stone towards changing the instantiate-to-bounds to choosing Object?, and achieving "no implicit dynamic".