feat(toastr): remove deprecated iconPack property

[yggg]

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Short description of what this resolves:

BREAKING CHANGE:
NbToastrConfig.iconPack property remove. You can set icon pack via icon property:

const toastrConfig = {
  // ...
  icon: { icon: 'star', pack: 'eva' },
}

NbToastComponent.iconPack and NbToastComponent.iconConfig properties removed.
Use icon property instead.