Ensure items disable when hitting max.

[BenHenning]

This PR updates oppia#4777 to ensure that the checkboxes are properly disabled when the max number of items is selected, and that they're visually updated to look disabled.

What it does not do that you'll need to do @Akshatkamboj14:

• Check with the design team on which color should be used for the disabled version (the current color seems to have too poor of a contrast).
• Update tests to verify that the behaviors are working as expected.
• Add tests for the new AppCompatCheckBoxBindingAdapters in a similar way to other adapters tests.
• Update 4777 to mark Introduce warning for selections oppia/oppia-android#3624 as fixed.

Note that I already checked the accessibility flow and it seems pretty solid.

[BenHenning]

PTAL @Akshatkamboj14.

[github-actions]

Thanks for submitting this pull request! Some main reviewers
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little while before we can look at this PR. We appreciate your
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