Feature Request: disable rules for whole file

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

New feature request

After the introduction of the blanket_disable_command rule in https://github.com/realm/SwiftLint/pull/4731, all disabled rules have to be re-enabled again, otherwise the rule produces a warning.

There are some use cases where a rule should not be active for a certain file, e.g. in a Package.swift file or test classes.

At the moment this makes it necessary to disable the rule at the top of the file and to enable it again at the end of the file.

The re-enabling at the end of the file just to avoid the blanket_disable_command warning seems cumbersome.

It would be nice to introduce a new :file specifier (analog to the existing :previous, :this or :next specifiers) to explicitly convey the intention, that a rule is disabled for the whole file and doesn't need to be re-enabled again.

I think this could also be used to partially solve some uses cases of https://github.com/realm/SwiftLint/issues/2355

// swiftlint:disable:file <rule1> [<rule2> <rule3>...]

Start with the existing blanket_disable_command rule and the handling of the :previous, :this, and :next specifiers. Trace how file-level disable and re-enable directives are parsed and validated, then define the expected behavior for a :file specifier using the example in the issue. Done means a file can disable selected rules without a matching re-enable directive and without a blanket-disable warning.