refactor: use Bootstrap modal instead of native confirm

[Veszter-007]

If a bootstrap modal exists in the DOM, use it, otherwise leave the native one.

<div class="modal fade" id="datagridConfirmModal" tabindex="-1">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Delete ?</h5>
                <button type="button" class="btn-close" data-bs-dismiss="modal"></button>
            </div>
            <div class="modal-body" id="datagridConfirmMessage"></div>
            <div class="modal-footer">
                <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Cancel</button>
                <button type="button" class="btn btn-danger" id="datagridConfirmOk">Delete</button>
            </div>
        </div>
    </div>
</div>