- always_declare_return_types
- annotate_overrides
- curly_braces_in_flow_control_structures
- prefer_for_elements_to_map_fromiterable
- prefer_if_null_operators
- prefer_single_quotes
- prefer_spread_collections
- unawaited_futures
- use_function_type_syntax_for_parameters

Rename a method starting with `get` to use a more accurately descriptive
verb.

Tighten the types on some methods highlighted by the
`always_declare_return_types` lint by making them generic instead of
returning `dynamic`.

Enable the `unnecessary_new` lint to prevent regressions.

Enabled a bunch of lints which are (hopefully) not controversial and fix
existing violations. Most of the fixes are pretty mechanical.

* Fix deprecated uses from cli_util
* Move analysis_options to the correct name

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2184303002 .