Sources under `packages/flutter_tools/` aren't accessible to the average
Flutter user by navigating through sources from their projects, so it
doesn't need to be as explicitly verbose with types for readability
purposes. The `always_specify_types` lint results in extremely verbose
code within the tool which adds little value.
This change disables `always_specify_types` in favor of a new set of
lints that aim to reduce verbosity by removing obvious types while also
maintaining readability in cases where variable types otherwise wouldn't
be obvious:
- `omit_obvious_local_variable_types`
- `omit_obvious_property_types`
- `specify_nonobvious_local_variable_types`
- `specify_nonobvious_property_types`
