Add many more global analyses. (#47875)

* Update packages.

* Add many more global analyses.

* Catch trailing spaces and trailing newlines in all text files.
  Before we were only checking newly added files, but that means we
  missed some.

* Port the trailing spaces logic to work on Windows too.

* Correct all the files with trailing spaces and newlines.

* Refactor some of the dev/bots logic into a utils.dart library.
  Notably, the "exit" and "print" shims for testing are now usable
  from test.dart, analyze.dart, and run_command.dart.

* Add an "exitWithError" function that prints the red lines and
  then exits. This is the preferred way to exit from test.dart,
  analyze.dart, and run_command.dart.

* More consistency in the output of analyze.dart.

* Refactor analyze.dart to use the _allFiles file enumerating logic
  more widely.

* Add some double-checking logic to the _allFiles logic to catch
  cases where changes to that logic end up catching fewer files
  than expected (helps prevent future false positives).

* Add a check to prevent new binary files from being added to
  the repository. Grandfather in the binaries that we've already
  added.

* Update all the dependencies (needed because we now import crypto in
  dev/bots/analyze.dart).

CONTRIBUTING.md

@@ -33,18 +33,18 @@ If you want to help us triage, you are very welcome to do so!
    that everyone must be gracious, respectful, and professional. If you're helping out
    with triage, you are representing the Flutter team, and so you want to make sure to
    make a good impression!
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+
 3. Help out as described in our wiki: https://github.com/flutter/flutter/wiki/Triage
    You won't be able to add labels at first, so instead start by trying to
    do the other steps, e.g. trying to reproduce the problem and asking for people to
    provide enough details that you can reproduce the problem, pointing out duplicates,
    and so on. Chat on the #hackers-triage channel to let us know what you're up to!
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 4. Familiarize yourself with our
    [issue hygiene](https://github.com/flutter/flutter/wiki/Issue-hygiene) wiki page,
    which covers the meanings of some important GitHub labels and
    milestones.
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 5. Once you've been doing this for a while, someone will invite you to the flutter-hackers
    team on GitHub and you'll be able to add labels too. See the
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