update the analysis options for tools/licenses

[devoncarew]

• update the analysis options for tools/licenses

This is an update to #27331; we need to do a little bit of work to the repo to reduce the number of analysis options files. This directory was using a different (and I assume much older) analysis options file from the rest of the repo.

cc @zanderso for review (unless there's someone more familiar with this area)

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[zanderso]

Thanks for this cleanup!

[zanderso]

Please avoid extension methods: https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#avoid-using-extension

[devoncarew]

It's an extension that's just used in this file. I can change the visibility to private and add a comment?

This is to get around a super odd type hierarchy in filesystem.dart.

I could also change this to a static helper method.

[devoncarew]

I updated the call sites to use a static helper method (instead of an extension method).

[zanderso]

lgtm