Add support for variant filtering

[cortinico]

📜 Description

This PR adds 3 fields to the extension to offer filtering capabilities for variant/buildtypes/flavors:

                sentry {
                  ignoredVariants = ["..."]
                  ignoredBuildTypes = ["..."]
                  ignoredFlavors = ["..."]
                }

I refactored a bit the tests and created a new VariantTest integration test to test only this (otherwise adding flavors to the original test would have complicated task names unnecessarily).

💡 Motivation and Context

Fixes #18

💚 How did you test it?

Integration tests are included

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• No breaking changes

[marandaneto]

nice, thanks for doing this @cortinico , looks great.