package_config

• Renamed readAnyConfigFile to readConfigFile, and removed
  the preferNewest parameter.
• Same for readAnyConfigFileUri which becomes readConfigFileUri.
• Old functions still exists as deprecated, forwarding to the new
  functions without the preferNewest argument.
  Makes PackageConfig, Package and LanguageVersion @sealed classes,
  in preparation for making them final in a future update.

Adds discovery API to find both a configuration and its location: findPackageConfigAndFile and findPackageConfigAndUri.

Removes support for the .packages file. The Dart SDK no longer supports that file, and no new .packages files will be generated. Since the SDK requirement for this package is above 3.0.0, no supporting SDK can use or generate .packages.

Simplifies API that no longer needs to support two separate files.

• Renamed readAnyConfigFile to readConfigFile, and removed the preferNewest parameter.
• Same for readAnyConfigFileUri which becomes readConfigFileUri.
• Old functions still exists as deprecated, forwarding to the new functions without the preferNewest argument.

Makes PackageConfig, Package and LanguageVersion @sealed classes, in preparation for making them final in a future update.

Adds PackageConfig.minVersion to complement .maxVersion. Currently both are 2.

Add relational operators to LanguageVersion with extension methods exported under LanguageVersionRelationalOperators.

Include correct parameter names in errors when validating the major and minor versions in the LanguageVersion.new constructor.

Adds minVersion to findPackageConfig and findPackageConfigVersion which allows ignoring earlier versions (which currently only means ignoring version 1, aka. .packages files.)

Changes the version number of SimplePackageConfig.empty to the current maximum version.

Improve file read performance; improve lookup performance.

Emit an error when a package is inside the package root of another package.

Fix a link in the readme.