enhancement(Datepicker) implementation with confirmation buttons util

[gselderslaghs]

Proposed changes

This pull request is a follow up of #571 and #574 and handles the implementation of the Utils.createButton with callback method and the Utils.createConfirmContainer with callback methods

Example with buttons

const input = document.querySelector('.datepicker');
M.Datepicker.init(input, {
    autoSubmit: false,
    showClearBtn: true
});

Example without buttons:

M.Datepicker.init(input, {
    autoSubmit: true,
    showClearBtn: false
});

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to change).

Checklist:

• I have read the CONTRIBUTING document.
• My commit messages follows the conventional commit format
• My change requires a change to the documentation, and updated it accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[gselderslaghs]

Changelog

• Refactored existing spec test to not depend on previously implemented confirm button interaction
• Implemented additional spec test on action util buttons integration by option