Support removing unused import in Vue.

Currently, removing unused imports is disabled for *.vue* files because imports can be used outside of `` ([link](https://vuejs.org/api/sfc-script-setup.html#using-components)) and there isn't an easy way to find them.

The feature request is to find a way to enable it.

Start by tracing the existing unused-import removal path and its special handling for *.vue files, then review the Vue SFC and script-setup usage linked in the issue. Define how template component references are identified and add coverage for safe removal; done means unused imports can be removed without deleting imports still used outside <script>.

Written by the indexing model from the issue text.