feat(prompts): Improve post-save prompt ux (#6093)

* feat(prompts): Update prompt combobox after save

Also reset dirty state on save

* Block page navigation when any instance is dirty

* Use native beforeunload dialog

* Aggresively re-fetch prompt combobox

This allows the prompt combobox to repopulate when new prompts are created,
but it also causes it to overfetch whenever you change prompts