[analytics] stop reporting data about context creation

[pq]

To motivate the refactoring to multi-option analysis contexts, we collected a bunch of data that is now no longer needed.

Specifically:

  /// The number of contexts that were created that have neither a packages nor
  /// an options file.
  final int contextsWithoutFiles;

  /// The number of contexts that were created that have a unique packages file
  /// and either no options file or an inherited options file.
  final int contextsFromPackagesFiles;

  /// The number of contexts that were created that have a unique options file
  /// and either no packages file or an inherited packages file.
  final int contextsFromOptionsFiles;

  /// The number of contexts that were created that have both a unique packages
  /// file and a unique options file.
  final int contextsFromBothFiles;

With that work complete, we no longer need the data and should stop reporting it.

[bwilkerson]

Closed by https://dart-review.googlesource.com/c/sdk/+/437126.