Impossible to use the #messageicon slot in the toast component

[jasverix]

Describe the bug

It is not possible to use the #messageicon slot now, because we don't know the message to be shown, so we cannot set the correct icon.

Pull Request Link

#8568

Reason for not contributing a PR

• Lack of time
• Unsure how to implement the fix/feature
• Difficulty understanding the codebase
• Other

Other Reason

No response

Reproducer

https://stackblitz.com/edit/primevue-4-vite-issue-template-q95bwmhv?file=src%2FApp.vue

Environment

Just a simple environment using toast.

Vue version

3.5.13

PrimeVue version

4.3.1

Node version

No response

Browser(s)

No response

Steps to reproduce the behavior

Create a toast. Try to make your own message icon.

Expected behavior

I want to be able to define an icon based on the message severity.