Add support on className to Checkbox&AttentionBox instead of componentClassName

[hadasfa]

Go over this checklist before submitting your Pull Request

Description: Add support on className to Checkbox&AttentionBox instead of componentClassName

Updating existing component

Basic

• [v] PR has description
• [] Changes to the component are backward compatible (including selectors structure). If not - add to the title of the PR "BREAKABLE_CHANGE""
• [v] All changes to the component are reflected in the ReadMe
• [v] If component is old and was not compliant with the latest guidelines - it was fixed (optional)

Style

• CSS selectors are named using BEM convention
• Design is compatible with Monday Design System

Storybook

• [ v] All the changes to the component should be reflected in the Storybook.
• [v ] Component passed Accessibility Plugin checks

Tests

• [ v] All current tests are passing
• [ v] New functionality is covered with tests
• [v ] Tests are compliant with TESTING_README.md instructions