[Enhancement]: error message when using `externsionAlias`

[SoonIter]

Summary

Related Links

https://github.com/web-infra-dev/rsbuild/pull/3536

without extensionAlias

rspack

webpack

with extensionAlias

  resolve: {
    extensionAlias: {
      '.js': ['.ts', '.tsx'],
    },
  },

rspack

webpack