Breaking change: Improved Directives Sorting Analysis

[Phil Quitslund]

As of the 2.14.0-52.0.dev build and 2.14 stable, the directives_ordering lint will catch a number of previously overlooked cases.  Some work was done to update Flutter and patch up downstream packages (see: dart-lang/linter#2609) but other consumers of this lint may see new violations.  The lint can be auto-fixed in IDEs (using the "Optimize Imports" action in IntelliJ for example) or on the command-line by using dart fix (e.g., dart fix --apply).

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Phil Quitslund

Software Engineer

Google, Inc.