Fixes #2723

In the spirit of https://github.com/flutter/flutter/issues/1220, remove the tear-off regexp in favor of in-line suppressions (if needed).

Runs clean on the repo.  Moving ahead, we can manage exceptions via `.analysis_options` or specific source-level ignores.

This patch renames StatelessComponent to StatelessWidget and
StatefulComponent to StatefulWidget.

Fixes #2308

And fix the zillion issues that uncovered.

This reverts commit f41b3411, reversing
changes made to e33d8d96.

This was a bad check-in due to my mangling uploading a new version of the branch from a different machine.

This reverts https://github.com/flutter/flutter/pull/2639 and will be replaced by https://github.com/flutter/flutter/pull/2640

And fix the zillion issues that uncovered.

More groundwork to get `analyze` and IDE output to agree.

See: https://github.com/dart-lang/sdk/issues/25723

Removing some special-casing in pursuit of aligning `flutter analyze` output with that provided by server/IDEs.  Specifically:
  * strong-hints (stale, no longer supported)
  * "analyzer says" comment handling in favor of `//ignore`s
  * `conflictingNamePattern` --- no longer needed

Next up some of the error filter regexps...

Well, all the easy ones, anyway.

For some reason `// ignore:` isn't working for me so I've disabled
lints that need that. Also disabled those that require a ton of work
(which I'm doing, but not in this PR, to keep it reviewable).

This adds:
- avoid_init_to_null
- library_names
- package_api_docs
- package_names
- package_prefixed_library_names
- prefer_is_not_empty
- sort_constructors_first
- sort_unnamed_constructors_first
- unnecessary_getters_setters

And fix a zillion omissions this uncovered.

Also, resolve our package conflict, since reflectable has been fixed.

It has performance implications in release mode.

We'll enable the lint once https://github.com/dart-lang/linter/issues/195 is fixed.

This is a variety of trivial fixes that I collected while going through the dartdocs.
This does contain some non-comment changes.

Also, handle the new directory structure of the flutter repo.

Migrates error suppression from regexps to analysis options.
* Ignore TODOs.
* Ignore strong mode field and method overrides (see `InvalidFieldOverride` and `InvalidMethodOverride` in `strong/info.dart`.
* Remove stale regexp to capture refs to dead `dart:ui_internals` URI.
* Remove stale regexp to capture dead strong mode "will need runtime check to cast to type" error (https://github.com/dart-lang/sdk/issues/24542).

5 regexp downs, another small handful (~4) to go! :)

Migrates error suppression from regexps to analysis options.
* Ignore TODOs.
* Ignore strong mode field and method overrides (see `InvalidFieldOverride` and `InvalidMethodOverride` in `strong/info.dart`.
* Remove stale regexp to capture refs to dead `dart:ui_internals` URI.
* Remove stale regexp to capture dead strong mode "will need runtime check to cast to type" error (https://github.com/dart-lang/sdk/issues/24542).

5 regexp downs, another small handful (~4) to go! :)

This enables us to exclude `library_names` pending a new stable SDK push (see notes: https://github.com/flutter/flutter/pull/1996).  Also excluded are a few lints who's feedback was just getting regexp'ed out.  Moving forward, this will allow us to selectively enable specific lints of interest as well.

This enables us to exclude `library_names` pending a new stable SDK push (see notes: https://github.com/flutter/flutter/pull/1996).  Also excluded are a few lints who's feedback was just getting regexp'ed out.  Moving forward, this will allow us to selectively enable specific lints of interest as well.

These classes now share more code and have feature parity.

rename to printTrace(), printStatus(), and printError()

Before we didn't know how to find the packages of random files. Now we do.