Resolves unexpected closure of nested modals when the parent is a Bootstrap modal

[blasferna]

When opening a formset modal on top of a main Bootstrap modal, currently pressing the Escape key closes both modals, the secondary and the main one.

This behavior is not the expected one, as the secondary modal should close when pressing Escape, but the main modal should remain open.

This Pull Request implements the necessary changes to fix this issue and achieve the expected behavior:

• The keydown.dismiss.bs.modal event is disabled when opening the formset modal, preventing it from closing when pressing Escape.
• The secondary modal closes correctly when pressing Escape.
• When closing the secondary modal, the keydown.dismiss.bs.modal event is re-enabled for the main Bootstrap modal.
• The main Bootstrap modal remains open when the secondary modal is closed by pressing Escape.