Feature: Support `iconPosition` for custom Toast icons

[romantrukhtanov]

Description

Currently, toast notifications allow passing a custom icon, but do not provide a public API to control the icon position inside the toast layout

This is limiting in cases where the icon should be:

• top-aligned for multi-line content
• placed on the right and vertically centered
• placed on the right and top-aligned

At the moment, this can only be done with custom className and CSS overrides, which makes the solution dependent on internal layout styles

Proposed API

Add an iconPosition option to toast API, for example:

• start-center
• start-top
• end-center
• end-top

Example:

toast.show({
  title: "Saved",
  children: "Changes have been published",
  icon: <Icon svg={Check} size={5} color="positive" />,
  iconPosition: "end-top",
});

Reproduction

I created a reproduction case showing that while toast supports a custom icon, its position can't be configured through public API and currently requires CSS overrides

CodeSandbox: https://codesandbox.io/p/devbox/reshaped-toast-icon-position-3-9-0-jvc9lh